from datetime import date, datetime, timedelta
from pandas.compat import range
from pandas import compat
import numpy as np

from pandas.tseries.tools import to_datetime
from pandas.tseries.timedeltas import to_timedelta
from pandas.core.common import ABCSeries, ABCDatetimeIndex

# import after tools, dateutil check
from dateutil.relativedelta import relativedelta, weekday
from dateutil.easter import easter
import pandas.tslib as tslib
from pandas.tslib import Timestamp, OutOfBoundsDatetime, Timedelta

import functools

__all__ = ['Day', 'BusinessDay', 'BDay', 'CustomBusinessDay', 'CDay',
           'CBMonthEnd','CBMonthBegin',
           'MonthBegin', 'BMonthBegin', 'MonthEnd', 'BMonthEnd',
           'BusinessHour',
           'YearBegin', 'BYearBegin', 'YearEnd', 'BYearEnd',
           'QuarterBegin', 'BQuarterBegin', 'QuarterEnd', 'BQuarterEnd',
           'LastWeekOfMonth', 'FY5253Quarter', 'FY5253',
           'Week', 'WeekOfMonth', 'Easter',
           'Hour', 'Minute', 'Second', 'Milli', 'Micro', 'Nano',
           'DateOffset']

# convert to/from datetime/timestamp to allow invalid Timestamp ranges to pass thru
def as_timestamp(obj):
    if isinstance(obj, Timestamp):
        return obj
    try:
        return Timestamp(obj)
    except (OutOfBoundsDatetime):
        pass
    return obj

def as_datetime(obj):
    f = getattr(obj,'to_pydatetime',None)
    if f is not None:
        obj = f()
    return obj

def apply_wraps(func):
    @functools.wraps(func)
    def wrapper(self, other):
        if other is tslib.NaT:
            return tslib.NaT
        elif isinstance(other, (timedelta, Tick, DateOffset)):
            # timedelta path
            return func(self, other)
        elif isinstance(other, (np.datetime64, datetime, date)):
            other = as_timestamp(other)

        tz = getattr(other, 'tzinfo', None)
        nano = getattr(other, 'nanosecond', 0)

        try:
            if self._adjust_dst and isinstance(other, Timestamp):
                other = other.tz_localize(None)

            result = func(self, other)
            if self._adjust_dst:
                result = tslib._localize_pydatetime(result, tz)

            result = Timestamp(result)
            if self.normalize:
                result = result.normalize()

            # nanosecond may be deleted depending on offset process
            if not self.normalize and nano != 0:
                if not isinstance(self, Nano) and result.nanosecond != nano:
                    if result.tz is not None:
                        # convert to UTC
                        value = tslib.tz_convert_single(result.value, 'UTC', result.tz)
                    else:
                        value = result.value
                    result = Timestamp(value + nano)

            if tz is not None and result.tzinfo is None:
                result = tslib._localize_pydatetime(result, tz)

        except OutOfBoundsDatetime:
            result = func(self, as_datetime(other))

            if self.normalize:
                # normalize_date returns normal datetime
                result = normalize_date(result)

            if tz is not None and result.tzinfo is None:
                result = tslib._localize_pydatetime(result, tz)

        return result
    return wrapper


def apply_index_wraps(func):
    @functools.wraps(func)
    def wrapper(self, other):
        result = func(self, other)
        if self.normalize:
            result  = result.to_period('D').to_timestamp()
        return result
    return wrapper

def _is_normalized(dt):
    if (dt.hour != 0 or dt.minute != 0 or dt.second != 0
        or dt.microsecond != 0 or getattr(dt, 'nanosecond', 0) != 0):
        return False
    return True

#----------------------------------------------------------------------
# DateOffset


class ApplyTypeError(TypeError):
    # sentinel class for catching the apply error to return NotImplemented
    pass


class CacheableOffset(object):
    _cacheable = True


class DateOffset(object):
    """
    Standard kind of date increment used for a date range.

    Works exactly like relativedelta in terms of the keyword args you
    pass in, use of the keyword n is discouraged-- you would be better
    off specifying n in the keywords you use, but regardless it is
    there for you. n is needed for DateOffset subclasses.

    DateOffets work as follows.  Each offset specify a set of dates
    that conform to the DateOffset.  For example, Bday defines this
    set to be the set of dates that are weekdays (M-F).  To test if a
    date is in the set of a DateOffset dateOffset we can use the
    onOffset method: dateOffset.onOffset(date).

    If a date is not on a valid date, the rollback and rollforward
    methods can be used to roll the date to the nearest valid date
    before/after the date.

    DateOffsets can be created to move dates forward a given number of
    valid dates.  For example, Bday(2) can be added to a date to move
    it two business days forward.  If the date does not start on a
    valid date, first it is moved to a valid date.  Thus psedo code
    is:

    def __add__(date):
      date = rollback(date) # does nothing if date is valid
      return date + <n number of periods>

    When a date offset is created for a negitive number of periods,
    the date is first rolled forward.  The pseudo code is:

    def __add__(date):
      date = rollforward(date) # does nothing is date is valid
      return date + <n number of periods>

    Zero presents a problem.  Should it roll forward or back?  We
    arbitrarily have it rollforward:

    date + BDay(0) == BDay.rollforward(date)

    Since 0 is a bit weird, we suggest avoiding its use.
    """
    _cacheable = False
    _normalize_cache = True
    _kwds_use_relativedelta = (
        'years', 'months', 'weeks', 'days',
        'year', 'month', 'week', 'day', 'weekday',
        'hour', 'minute', 'second', 'microsecond'
        )
    _use_relativedelta = False
    _adjust_dst = False

    # default for prior pickles
    normalize = False

    def __init__(self, n=1, normalize=False, **kwds):
        self.n = int(n)
        self.normalize = normalize
        self.kwds = kwds
        self._offset, self._use_relativedelta = self._determine_offset()

    def _determine_offset(self):
        # timedelta is used for sub-daily plural offsets and all singular offsets
        # relativedelta is used for plural offsets of daily length or more
        # nanosecond(s) are handled by apply_wraps
        kwds_no_nanos = dict(
            (k, v) for k, v in self.kwds.items()
            if k not in ('nanosecond', 'nanoseconds')
            )
        use_relativedelta = False

        if len(kwds_no_nanos) > 0:
            if any(k in self._kwds_use_relativedelta for k in kwds_no_nanos):
                use_relativedelta = True
                offset = relativedelta(**kwds_no_nanos)
            else:
                # sub-daily offset - use timedelta (tz-aware)
                offset = timedelta(**kwds_no_nanos)
        else:
            offset = timedelta(1)
        return offset, use_relativedelta

    @apply_wraps
    def apply(self, other):
        if self._use_relativedelta:
            other = as_datetime(other)

        if len(self.kwds) > 0:
            tzinfo = getattr(other, 'tzinfo', None)
            if tzinfo is not None and self._use_relativedelta:
                # perform calculation in UTC
                other = other.replace(tzinfo=None)

            if self.n > 0:
                for i in range(self.n):
                    other = other + self._offset
            else:
                for i in range(-self.n):
                    other = other - self._offset

            if tzinfo is not None and self._use_relativedelta:
                # bring tz back from UTC calculation
                other = tslib._localize_pydatetime(other, tzinfo)

            return as_timestamp(other)
        else:
            return other + timedelta(self.n)

    @apply_index_wraps
    def apply_index(self, i):
        """
        Vectorized apply of DateOffset to DatetimeIndex,
        raises NotImplentedError for offsets without a
        vectorized implementation

        .. versionadded:: 0.17.0

        Parameters
        ----------
        i : DatetimeIndex

        Returns
        -------
        y : DatetimeIndex
        """

        if not type(self) is DateOffset:
            raise NotImplementedError("DateOffset subclass %s "
                                     "does not have a vectorized "
                                     "implementation"
                                     % (self.__class__.__name__,))
        relativedelta_fast = set(['years', 'months', 'weeks',
                                'days', 'hours', 'minutes',
                                'seconds', 'microseconds'])
        # relativedelta/_offset path only valid for base DateOffset
        if (self._use_relativedelta and
            set(self.kwds).issubset(relativedelta_fast)):

            months = ((self.kwds.get('years', 0) * 12
                        + self.kwds.get('months', 0)) * self.n)
            if months:
                shifted = tslib.shift_months(i.asi8, months)
                i = i._shallow_copy(shifted)

            weeks = (self.kwds.get('weeks', 0)) * self.n
            if weeks:
                i = (i.to_period('W') + weeks).to_timestamp() + i.to_perioddelta('W')

            timedelta_kwds = dict((k,v) for k,v in self.kwds.items()
                                    if k in ['days','hours','minutes',
                                            'seconds','microseconds'])
            if timedelta_kwds:
                delta = Timedelta(**timedelta_kwds)
                i = i + (self.n * delta)
            return i
        elif not self._use_relativedelta and hasattr(self, '_offset'):
            # timedelta
            return i + (self._offset * self.n)
        else:
            # relativedelta with other keywords
            raise NotImplementedError("DateOffset with relativedelta "
                                      "keyword(s) %s not able to be "
                                      "applied vectorized" %
                                      (set(self.kwds) - relativedelta_fast),)

    def isAnchored(self):
        return (self.n == 1)

    def copy(self):
        return self.__class__(self.n, normalize=self.normalize, **self.kwds)

    def _should_cache(self):
        return self.isAnchored() and self._cacheable

    def _params(self):
        all_paras = dict(list(vars(self).items()) + list(self.kwds.items()))
        if 'holidays' in all_paras and not all_paras['holidays']:
            all_paras.pop('holidays')
        exclude = ['kwds', 'name','normalize', 'calendar']
        attrs = [(k, v) for k, v in all_paras.items() if (k not in exclude ) and (k[0] != '_')]
        attrs = sorted(set(attrs))
        params = tuple([str(self.__class__)] + attrs)
        return params

    def __repr__(self):
        if hasattr(self, '_named'):
            return self._named
        className = getattr(self, '_outputName', type(self).__name__)
        exclude = set(['n', 'inc', 'normalize'])
        attrs = []
        for attr in sorted(self.__dict__):
            if ((attr == 'kwds' and len(self.kwds) == 0)
                    or attr.startswith('_')):
                continue
            elif attr == 'kwds':
                kwds_new = {}
                for key in self.kwds:
                    if not hasattr(self, key):
                        kwds_new[key] = self.kwds[key]
                if len(kwds_new) > 0:
                    attrs.append('='.join((attr, repr(kwds_new))))
            else:
                if attr not in exclude:
                    attrs.append('='.join((attr, repr(getattr(self, attr)))))

        if abs(self.n) != 1:
            plural = 's'
        else:
            plural = ''

        n_str = ""
        if self.n != 1:
            n_str = "%s * " % self.n

        out = '<%s' % n_str + className + plural
        if attrs:
            out += ': ' + ', '.join(attrs)
        out += '>'
        return out

    @property
    def name(self):
        if hasattr(self, '_named'):
            return self._named
        else:
            return self.rule_code

    def __eq__(self, other):
        if other is None:
            return False

        if isinstance(other, compat.string_types):
            from pandas.tseries.frequencies import to_offset

            other = to_offset(other)

        if not isinstance(other, DateOffset):
            return False

        return self._params() == other._params()

    def __ne__(self, other):
        return not self == other

    def __hash__(self):
        return hash(self._params())

    def __call__(self, other):
        return self.apply(other)

    def __add__(self, other):
        if isinstance(other, (ABCDatetimeIndex, ABCSeries)):
            return other + self
        try:
            return self.apply(other)
        except ApplyTypeError:
            return NotImplemented

    def __radd__(self, other):
        return self.__add__(other)

    def __sub__(self, other):
        if isinstance(other, datetime):
            raise TypeError('Cannot subtract datetime from offset.')
        elif type(other) == type(self):
            return self.__class__(self.n - other.n, normalize=self.normalize, **self.kwds)
        else:  # pragma: no cover
            return NotImplemented

    def __rsub__(self, other):
        if isinstance(other, (ABCDatetimeIndex, ABCSeries)):
            return other - self
        return self.__class__(-self.n, normalize=self.normalize, **self.kwds) + other

    def __mul__(self, someInt):
        return self.__class__(n=someInt * self.n, normalize=self.normalize, **self.kwds)

    def __rmul__(self, someInt):
        return self.__mul__(someInt)

    def __neg__(self):
        return self.__class__(-self.n, normalize=self.normalize, **self.kwds)

    def rollback(self, dt):
        """Roll provided date backward to next offset only if not on offset"""
        dt = as_timestamp(dt)
        if not self.onOffset(dt):
            dt = dt - self.__class__(1, normalize=self.normalize, **self.kwds)
        return dt

    def rollforward(self, dt):
        """Roll provided date forward to next offset only if not on offset"""
        dt = as_timestamp(dt)
        if not self.onOffset(dt):
            dt = dt + self.__class__(1, normalize=self.normalize, **self.kwds)
        return dt

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        # XXX, see #1395
        if type(self) == DateOffset or isinstance(self, Tick):
            return True

        # Default (slow) method for determining if some date is a member of the
        # date range generated by this offset. Subclasses may have this
        # re-implemented in a nicer way.
        a = dt
        b = ((dt + self) - self)
        return a == b

    # helpers for vectorized offsets
    def _beg_apply_index(self, i, freq):
        """Offsets index to beginning of Period frequency"""

        off = i.to_perioddelta('D')

        from pandas.tseries.frequencies import get_freq_code
        base, mult = get_freq_code(freq)
        base_period = i.to_period(base)
        if self.n < 0:
            # when subtracting, dates on start roll to prior
            roll = np.where(base_period.to_timestamp() == i - off,
                            self.n, self.n + 1)
        else:
            roll = self.n

        base = (base_period + roll).to_timestamp()
        return base + off

    def _end_apply_index(self, i, freq):
        """Offsets index to end of Period frequency"""

        off = i.to_perioddelta('D')

        import pandas.tseries.frequencies as frequencies
        from pandas.tseries.frequencies import get_freq_code
        base, mult = get_freq_code(freq)
        base_period = i.to_period(base)
        if self.n > 0:
            # when adding, dtates on end roll to next
            roll = np.where(base_period.to_timestamp(how='end') == i - off,
                            self.n, self.n - 1)
        else:
            roll = self.n

        base = (base_period + roll).to_timestamp(how='end')
        return base + off

    # way to get around weirdness with rule_code
    @property
    def _prefix(self):
        raise NotImplementedError('Prefix not defined')

    @property
    def rule_code(self):
        return self._prefix

    @property
    def freqstr(self):
        try:
            code = self.rule_code
        except NotImplementedError:
            return repr(self)

        if self.n != 1:
            fstr = '%d%s' % (self.n, code)
        else:
            fstr = code

        return fstr

class SingleConstructorOffset(DateOffset):

    @classmethod
    def _from_name(cls, suffix=None):
        # default _from_name calls cls with no args
        if suffix:
            raise ValueError("Bad freq suffix %s" % suffix)
        return cls()

class BusinessMixin(object):
    """ mixin to business types to provide related functions """

    # TODO: Combine this with DateOffset by defining a whitelisted set of
    # attributes on each object rather than the existing behavior of iterating
    # over internal ``__dict__``
    def __repr__(self):
        if hasattr(self, '_named'):
            return self._named
        className = getattr(self, '_outputName', self.__class__.__name__)

        if abs(self.n) != 1:
            plural = 's'
        else:
            plural = ''

        n_str = ""
        if self.n != 1:
            n_str = "%s * " % self.n

        out = '<%s' % n_str + className + plural + self._repr_attrs() + '>'
        return out

    def _repr_attrs(self):
        if self.offset:
            attrs = ['offset=%s' % repr(self.offset)]
        else:
            attrs = None
        out = ''
        if attrs:
            out += ': ' + ', '.join(attrs)
        return out

class BusinessDay(BusinessMixin, SingleConstructorOffset):
    """
    DateOffset subclass representing possibly n business days
    """
    _prefix = 'B'
    _adjust_dst = True

    def __init__(self, n=1, normalize=False, **kwds):
        self.n = int(n)
        self.normalize = normalize
        self.kwds = kwds
        self.offset = kwds.get('offset', timedelta(0))

    @property
    def freqstr(self):
        try:
            code = self.rule_code
        except NotImplementedError:
            return repr(self)

        if self.n != 1:
            fstr = '%d%s' % (self.n, code)
        else:
            fstr = code

        if self.offset:
            fstr += self._offset_str()

        return fstr

    def _offset_str(self):
        def get_str(td):
            off_str = ''
            if td.days > 0:
                off_str += str(td.days) + 'D'
            if td.seconds > 0:
                s = td.seconds
                hrs = int(s / 3600)
                if hrs != 0:
                    off_str += str(hrs) + 'H'
                    s -= hrs * 3600
                mts = int(s / 60)
                if mts != 0:
                    off_str += str(mts) + 'Min'
                    s -= mts * 60
                if s != 0:
                    off_str += str(s) + 's'
            if td.microseconds > 0:
                off_str += str(td.microseconds) + 'us'
            return off_str

        if isinstance(self.offset, timedelta):
            zero = timedelta(0, 0, 0)
            if self.offset >= zero:
                off_str = '+' + get_str(self.offset)
            else:
                off_str = '-' + get_str(-self.offset)
            return off_str
        else:
            return '+' + repr(self.offset)

    def isAnchored(self):
        return (self.n == 1)

    @apply_wraps
    def apply(self, other):
        if isinstance(other, datetime):
            n = self.n

            if n == 0 and other.weekday() > 4:
                n = 1

            result = other

            # avoid slowness below
            if abs(n) > 5:
                k = n // 5
                result = result + timedelta(7 * k)
                if n < 0 and result.weekday() > 4:
                    n += 1
                n -= 5 * k
                if n == 0 and result.weekday() > 4:
                    n -= 1

            while n != 0:
                k = n // abs(n)
                result = result + timedelta(k)
                if result.weekday() < 5:
                    n -= k

            if self.offset:
                result = result + self.offset
            return result

        elif isinstance(other, (timedelta, Tick)):
            return BDay(self.n, offset=self.offset + other,
                        normalize=self.normalize)
        else:
            raise ApplyTypeError('Only know how to combine business day with '
                                 'datetime or timedelta.')

    @apply_index_wraps
    def apply_index(self, i):
        time = i.to_perioddelta('D')
        # to_period rolls forward to next BDay; track and
        # reduce n where it does when rolling forward
        shifted = (i.to_perioddelta('B') - time).asi8 != 0
        if self.n > 0:
            roll = np.where(shifted, self.n - 1, self.n)
        else:
            roll = self.n

        return (i.to_period('B') + roll).to_timestamp() + time

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        return dt.weekday() < 5


class BusinessHour(BusinessMixin, SingleConstructorOffset):
    """
    DateOffset subclass representing possibly n business days

    .. versionadded: 0.16.1

    """
    _prefix = 'BH'
    _anchor = 0

    def __init__(self, n=1, normalize=False, **kwds):
        self.n = int(n)
        self.normalize = normalize

        # must be validated here to equality check
        kwds['start'] = self._validate_time(kwds.get('start', '09:00'))
        kwds['end'] = self._validate_time(kwds.get('end', '17:00'))
        self.kwds = kwds
        self.offset = kwds.get('offset', timedelta(0))
        self.start = kwds.get('start', '09:00')
        self.end = kwds.get('end', '17:00')

        # used for moving to next businessday
        if self.n >= 0:
            self.next_bday = BusinessDay(n=1)
        else:
            self.next_bday = BusinessDay(n=-1)

    def _validate_time(self, t_input):
        from datetime import time as dt_time
        import time
        if isinstance(t_input, compat.string_types):
            try:
                t = time.strptime(t_input, '%H:%M')
                return dt_time(hour=t.tm_hour, minute=t.tm_min)
            except ValueError:
                raise ValueError("time data must match '%H:%M' format")
        elif isinstance(t_input, dt_time):
            if t_input.second != 0 or t_input.microsecond != 0:
                raise ValueError("time data must be specified only with hour and minute")
            return t_input
        else:
            raise ValueError("time data must be string or datetime.time")

    def _get_daytime_flag(self):
        if self.start == self.end:
            raise ValueError('start and end must not be the same')
        elif self.start < self.end:
            return True
        else:
            return False

    def _repr_attrs(self):
        out = super(BusinessHour, self)._repr_attrs()
        attrs = ['BH=%s-%s' % (self.start.strftime('%H:%M'),
                               self.end.strftime('%H:%M'))]
        out += ': ' + ', '.join(attrs)
        return out

    def _next_opening_time(self, other):
        """
        If n is positive, return tomorrow's business day opening time.
        Otherwise yesterday's business day's opening time.

        Opening time always locates on BusinessDay.
        Otherwise, closing time may not if business hour extends over midnight.
        """
        if not self.next_bday.onOffset(other):
            other = other + self.next_bday
        else:
            if self.n >= 0 and self.start < other.time():
                other = other + self.next_bday
            elif self.n < 0 and other.time() < self.start:
                other = other + self.next_bday
        return datetime(other.year, other.month, other.day,
                        self.start.hour, self.start.minute)

    def _prev_opening_time(self, other):
        """
        If n is positive, return yesterday's business day opening time.
        Otherwise yesterday business day's opening time.
        """
        if not self.next_bday.onOffset(other):
            other = other - self.next_bday
        else:
            if self.n >= 0 and other.time() < self.start:
                other = other - self.next_bday
            elif self.n < 0 and other.time() > self.start:
                other = other - self.next_bday
        return datetime(other.year, other.month, other.day,
                        self.start.hour, self.start.minute)

    def _get_business_hours_by_sec(self):
        """
        Return business hours in a day by seconds.
        """
        if self._get_daytime_flag():
            # create dummy datetime to calcurate businesshours in a day
            dtstart = datetime(2014, 4, 1, self.start.hour, self.start.minute)
            until = datetime(2014, 4, 1, self.end.hour, self.end.minute)
            return tslib.tot_seconds(until - dtstart)
        else:
            self.daytime = False
            dtstart = datetime(2014, 4, 1, self.start.hour, self.start.minute)
            until = datetime(2014, 4, 2, self.end.hour, self.end.minute)
            return tslib.tot_seconds(until - dtstart)

    @apply_wraps
    def rollback(self, dt):
        """Roll provided date backward to next offset only if not on offset"""
        if not self.onOffset(dt):
            businesshours = self._get_business_hours_by_sec()
            if self.n >= 0:
                dt = self._prev_opening_time(dt) + timedelta(seconds=businesshours)
            else:
                dt = self._next_opening_time(dt) + timedelta(seconds=businesshours)
        return dt

    @apply_wraps
    def rollforward(self, dt):
        """Roll provided date forward to next offset only if not on offset"""
        if not self.onOffset(dt):
            if self.n >= 0:
                return self._next_opening_time(dt)
            else:
                return self._prev_opening_time(dt)
        return dt

    @apply_wraps
    def apply(self, other):
        # calcurate here because offset is not immutable
        daytime = self._get_daytime_flag()
        businesshours = self._get_business_hours_by_sec()
        bhdelta = timedelta(seconds=businesshours)

        if isinstance(other, datetime):
            # used for detecting edge condition
            nanosecond = getattr(other, 'nanosecond', 0)
            # reset timezone and nanosecond
            # other may be a Timestamp, thus not use replace
            other = datetime(other.year, other.month, other.day,
                             other.hour, other.minute,
                             other.second, other.microsecond)
            n = self.n
            if n >= 0:
                if (other.time() == self.end or
                    not self._onOffset(other, businesshours)):
                    other = self._next_opening_time(other)
            else:
                if other.time() == self.start:
                    # adjustment to move to previous business day
                    other = other - timedelta(seconds=1)
                if not self._onOffset(other, businesshours):
                    other = self._next_opening_time(other)
                    other = other + bhdelta

            bd, r = divmod(abs(n * 60), businesshours // 60)
            if n < 0:
                bd, r = -bd, -r

            if bd != 0:
                skip_bd = BusinessDay(n=bd)
                # midnight busienss hour may not on BusinessDay
                if not self.next_bday.onOffset(other):
                    remain = other - self._prev_opening_time(other)
                    other = self._next_opening_time(other + skip_bd) + remain
                else:
                    other = other + skip_bd

            hours, minutes = divmod(r, 60)
            result = other + timedelta(hours=hours, minutes=minutes)

            # because of previous adjustment, time will be larger than start
            if ((daytime and (result.time() < self.start or self.end < result.time())) or
                not daytime and (self.end < result.time() < self.start)):
                if n >= 0:
                    bday_edge = self._prev_opening_time(other)
                    bday_edge = bday_edge + bhdelta
                    # calcurate remainder
                    bday_remain = result - bday_edge
                    result = self._next_opening_time(other)
                    result += bday_remain
                else:
                    bday_edge = self._next_opening_time(other)
                    bday_remain = result - bday_edge
                    result = self._next_opening_time(result) + bhdelta
                    result += bday_remain
            # edge handling
            if n >= 0:
                if result.time() == self.end:
                    result = self._next_opening_time(result)
            else:
                if result.time() == self.start and nanosecond == 0:
                    # adjustment to move to previous business day
                    result = self._next_opening_time(result- timedelta(seconds=1)) +bhdelta

            return result
        else:
            raise ApplyTypeError('Only know how to combine business hour with ')

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False

        if dt.tzinfo is not None:
            dt = datetime(dt.year, dt.month, dt.day, dt.hour,
                          dt.minute, dt.second, dt.microsecond)
        # Valid BH can be on the different BusinessDay during midnight
        # Distinguish by the time spent from previous opening time
        businesshours = self._get_business_hours_by_sec()
        return self._onOffset(dt, businesshours)

    def _onOffset(self, dt, businesshours):
        """
        Slight speedups using calcurated values
        """
        # if self.normalize and not _is_normalized(dt):
        #     return False
        # Valid BH can be on the different BusinessDay during midnight
        # Distinguish by the time spent from previous opening time
        if self.n >= 0:
            op = self._prev_opening_time(dt)
        else:
            op = self._next_opening_time(dt)
        span = tslib.tot_seconds(dt - op)
        if span <= businesshours:
            return True
        else:
            return False


class CustomBusinessDay(BusinessDay):
    """
    **EXPERIMENTAL** DateOffset subclass representing possibly n business days
    excluding holidays

    .. warning:: EXPERIMENTAL

        This class is not officially supported and the API is likely to change
        in future versions. Use this at your own risk.

    Parameters
    ----------
    n : int, default 1
    offset : timedelta, default timedelta(0)
    normalize : bool, default False
        Normalize start/end dates to midnight before generating date range
    weekmask : str, Default 'Mon Tue Wed Thu Fri'
        weekmask of valid business days, passed to ``numpy.busdaycalendar``
    holidays : list
        list/array of dates to exclude from the set of valid business days,
        passed to ``numpy.busdaycalendar``
    calendar : pd.HolidayCalendar or np.busdaycalendar
    """
    _cacheable = False
    _prefix = 'C'

    def __init__(self, n=1, normalize=False, weekmask='Mon Tue Wed Thu Fri',
                 holidays=None, calendar=None, **kwds):
        self.n = int(n)
        self.normalize = normalize
        self.kwds = kwds
        self.offset = kwds.get('offset', timedelta(0))
        calendar, holidays = self.get_calendar(weekmask=weekmask,
                                                         holidays=holidays,
                                                         calendar=calendar)
        # CustomBusinessDay instances are identified by the
        # following two attributes. See DateOffset._params()
        # holidays, weekmask

        self.kwds['weekmask'] = self.weekmask = weekmask
        self.kwds['holidays'] = self.holidays = holidays
        self.kwds['calendar'] = self.calendar = calendar

    def get_calendar(self, weekmask, holidays, calendar):
        '''Generate busdaycalendar'''
        if isinstance(calendar, np.busdaycalendar):
            if not holidays:
                holidays = tuple(calendar.holidays)
            elif not isinstance(holidays, tuple):
                holidays = tuple(holidays)
            else:
                 # trust that calendar.holidays and holidays are
                 # consistent
                pass
            return calendar, holidays

        if holidays is None:
            holidays = []
        try:
            holidays = holidays + calendar.holidays().tolist()
        except AttributeError:
            pass
        holidays = [self._to_dt64(dt, dtype='datetime64[D]') for dt in
                    holidays]
        holidays = tuple(sorted(holidays))

        kwargs = {'weekmask': weekmask}
        if holidays:
            kwargs['holidays'] = holidays

        try:
            busdaycalendar = np.busdaycalendar(**kwargs)
        except:
            # Check we have the required numpy version
            from distutils.version import LooseVersion

            if LooseVersion(np.__version__) < '1.7.0':
                raise NotImplementedError("CustomBusinessDay requires numpy >= "
                                          "1.7.0. Current version: " +
                                          np.__version__)
            else:
                raise
        return busdaycalendar, holidays

    def __getstate__(self):
        """Return a pickleable state"""
        state = self.__dict__.copy()
        del state['calendar']

        # we don't want to actually pickle the calendar object
        # as its a np.busyday; we recreate on deserilization
        try:
            state['kwds'].pop('calendar')
        except:
            pass

        return state

    def __setstate__(self, state):
        """Reconstruct an instance from a pickled state"""
        self.__dict__ = state
        calendar, holidays = self.get_calendar(weekmask=self.weekmask,
                                               holidays=self.holidays,
                                               calendar=None)
        self.kwds['calendar'] = self.calendar = calendar
        self.kwds['holidays'] = self.holidays = holidays
        self.kwds['weekmask'] = state['weekmask']

    @apply_wraps
    def apply(self, other):
        if self.n <= 0:
            roll = 'forward'
        else:
            roll = 'backward'

        if isinstance(other, datetime):
            date_in = other
            np_dt = np.datetime64(date_in.date())

            np_incr_dt = np.busday_offset(np_dt, self.n, roll=roll,
                                  busdaycal=self.calendar)

            dt_date = np_incr_dt.astype(datetime)
            result = datetime.combine(dt_date, date_in.time())

            if self.offset:
                result = result + self.offset
            return result

        elif isinstance(other, (timedelta, Tick)):
            return BDay(self.n, offset=self.offset + other,
                        normalize=self.normalize)
        else:
            raise ApplyTypeError('Only know how to combine trading day with '
                                 'datetime, datetime64 or timedelta.')

    def apply_index(self, i):
        raise NotImplementedError

    @staticmethod
    def _to_dt64(dt, dtype='datetime64'):
        # Currently
        # > np.datetime64(dt.datetime(2013,5,1),dtype='datetime64[D]')
        # numpy.datetime64('2013-05-01T02:00:00.000000+0200')
        # Thus astype is needed to cast datetime to datetime64[D]
        if getattr(dt, 'tzinfo', None) is not None:
            i8 = tslib.pydt_to_i8(dt)
            dt = tslib.tz_convert_single(i8, 'UTC', dt.tzinfo)
            dt = Timestamp(dt)
        dt = np.datetime64(dt)
        if dt.dtype.name != dtype:
            dt = dt.astype(dtype)
        return dt

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        day64 = self._to_dt64(dt,'datetime64[D]')
        return np.is_busday(day64, busdaycal=self.calendar)


class MonthOffset(SingleConstructorOffset):
    _adjust_dst = True

    @property
    def name(self):
        if self.isAnchored:
            return self.rule_code
        else:
            return "%s-%s" % (self.rule_code, _int_to_month[self.n])


class MonthEnd(MonthOffset):
    """DateOffset of one month end"""

    @apply_wraps
    def apply(self, other):
        n = self.n
        _, days_in_month = tslib.monthrange(other.year, other.month)
        if other.day != days_in_month:
            other = other + relativedelta(months=-1, day=31)
            if n <= 0:
                n = n + 1
        other = other + relativedelta(months=n, day=31)
        return other

    @apply_index_wraps
    def apply_index(self, i):
        months = self.n - 1 if self.n >= 0 else self.n
        shifted = tslib.shift_months(i.asi8, months, 'end')
        return i._shallow_copy(shifted)

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        days_in_month = tslib.monthrange(dt.year, dt.month)[1]
        return dt.day == days_in_month

    _prefix = 'M'


class MonthBegin(MonthOffset):
    """DateOffset of one month at beginning"""

    @apply_wraps
    def apply(self, other):
        n = self.n

        if other.day > 1 and n <= 0:  # then roll forward if n<=0
            n += 1

        return other + relativedelta(months=n, day=1)

    @apply_index_wraps
    def apply_index(self, i):
        months = self.n + 1 if self.n < 0 else self.n
        shifted = tslib.shift_months(i.asi8, months, 'start')
        return i._shallow_copy(shifted)

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        return dt.day == 1

    _prefix = 'MS'


class BusinessMonthEnd(MonthOffset):
    """DateOffset increments between business EOM dates"""

    def isAnchored(self):
        return (self.n == 1)

    @apply_wraps
    def apply(self, other):
        n = self.n
        wkday, days_in_month = tslib.monthrange(other.year, other.month)
        lastBDay = days_in_month - max(((wkday + days_in_month - 1)
                                        % 7) - 4, 0)

        if n > 0 and not other.day >= lastBDay:
            n = n - 1
        elif n <= 0 and other.day > lastBDay:
            n = n + 1
        other = other + relativedelta(months=n, day=31)

        if other.weekday() > 4:
            other = other - BDay()
        return other

    _prefix = 'BM'


class BusinessMonthBegin(MonthOffset):
    """DateOffset of one business month at beginning"""

    @apply_wraps
    def apply(self, other):
        n = self.n
        wkday, _ = tslib.monthrange(other.year, other.month)
        first = _get_firstbday(wkday)

        if other.day > first and n <= 0:
            # as if rolled forward already
            n += 1
        elif other.day < first and n > 0:
            other = other + timedelta(days=first - other.day)
            n -= 1

        other = other + relativedelta(months=n)
        wkday, _ = tslib.monthrange(other.year, other.month)
        first = _get_firstbday(wkday)
        result = datetime(other.year, other.month, first, other.hour, other.minute,
                          other.second, other.microsecond)
        return result

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        first_weekday, _ = tslib.monthrange(dt.year, dt.month)
        if first_weekday == 5:
            return dt.day == 3
        elif first_weekday == 6:
            return dt.day == 2
        else:
            return dt.day == 1

    _prefix = 'BMS'


class CustomBusinessMonthEnd(BusinessMixin, MonthOffset):
    """
    **EXPERIMENTAL** DateOffset of one custom business month

    .. warning:: EXPERIMENTAL

        This class is not officially supported and the API is likely to change
        in future versions. Use this at your own risk.

    Parameters
    ----------
    n : int, default 1
    offset : timedelta, default timedelta(0)
    normalize : bool, default False
        Normalize start/end dates to midnight before generating date range
    weekmask : str, Default 'Mon Tue Wed Thu Fri'
        weekmask of valid business days, passed to ``numpy.busdaycalendar``
    holidays : list
        list/array of dates to exclude from the set of valid business days,
        passed to ``numpy.busdaycalendar``
    calendar : pd.HolidayCalendar or np.busdaycalendar
    """

    _cacheable = False
    _prefix = 'CBM'
    def __init__(self, n=1, normalize=False,  weekmask='Mon Tue Wed Thu Fri',
                 holidays=None, calendar=None, **kwds):
        self.n = int(n)
        self.normalize = normalize
        self.kwds = kwds
        self.offset = kwds.get('offset', timedelta(0))
        self.cbday = CustomBusinessDay(n=self.n, normalize=normalize,
                                       weekmask=weekmask, holidays=holidays,
                                       calendar=calendar, **kwds)
        self.m_offset = MonthEnd(n=1, normalize=normalize, **kwds)
        self.kwds['calendar'] = self.cbday.calendar  # cache numpy calendar

    @apply_wraps
    def apply(self,other):
        n = self.n
        # First move to month offset
        cur_mend = self.m_offset.rollforward(other)
        # Find this custom month offset
        cur_cmend = self.cbday.rollback(cur_mend)

        # handle zero case. arbitrarily rollforward
        if n == 0 and other != cur_cmend:
            n += 1

        if other < cur_cmend and n >= 1:
            n -= 1
        elif other > cur_cmend and n <= -1:
            n += 1

        new = cur_mend + n * self.m_offset
        result = self.cbday.rollback(new)
        return result

class CustomBusinessMonthBegin(BusinessMixin, MonthOffset):
    """
    **EXPERIMENTAL** DateOffset of one custom business month

    .. warning:: EXPERIMENTAL

        This class is not officially supported and the API is likely to change
        in future versions. Use this at your own risk.

    Parameters
    ----------
    n : int, default 1
    offset : timedelta, default timedelta(0)
    normalize : bool, default False
        Normalize start/end dates to midnight before generating date range
    weekmask : str, Default 'Mon Tue Wed Thu Fri'
        weekmask of valid business days, passed to ``numpy.busdaycalendar``
    holidays : list
        list/array of dates to exclude from the set of valid business days,
        passed to ``numpy.busdaycalendar``
    calendar : pd.HolidayCalendar or np.busdaycalendar
    """

    _cacheable = False
    _prefix = 'CBMS'
    def __init__(self, n=1, normalize=False,  weekmask='Mon Tue Wed Thu Fri',
                 holidays=None, calendar=None, **kwds):
        self.n = int(n)
        self.normalize = normalize
        self.kwds = kwds
        self.offset = kwds.get('offset', timedelta(0))
        self.cbday = CustomBusinessDay(n=self.n, normalize=normalize,
                                       weekmask=weekmask, holidays=holidays,
                                       calendar=calendar, **kwds)
        self.m_offset = MonthBegin(n=1, normalize=normalize, **kwds)
        self.kwds['calendar'] = self.cbday.calendar  # cache numpy calendar

    @apply_wraps
    def apply(self,other):
        n = self.n
        dt_in = other
        # First move to month offset
        cur_mbegin = self.m_offset.rollback(dt_in)
        # Find this custom month offset
        cur_cmbegin = self.cbday.rollforward(cur_mbegin)

        # handle zero case. arbitrarily rollforward
        if n == 0 and dt_in != cur_cmbegin:
            n += 1

        if dt_in > cur_cmbegin and n <= -1:
            n += 1
        elif dt_in < cur_cmbegin and n >= 1:
            n -= 1

        new = cur_mbegin + n * self.m_offset
        result = self.cbday.rollforward(new)
        return result

class Week(DateOffset):
    """
    Weekly offset

    Parameters
    ----------
    weekday : int, default None
        Always generate specific day of week. 0 for Monday
    """
    _adjust_dst = True
    def __init__(self, n=1, normalize=False, **kwds):
        self.n = n
        self.normalize = normalize
        self.weekday = kwds.get('weekday', None)

        if self.weekday is not None:
            if self.weekday < 0 or self.weekday > 6:
                raise ValueError('Day must be 0<=day<=6, got %d' %
                                 self.weekday)

        self._inc = timedelta(weeks=1)
        self.kwds = kwds

    def isAnchored(self):
        return (self.n == 1 and self.weekday is not None)

    @apply_wraps
    def apply(self, other):
        base = other
        if self.weekday is None:
            return other + self.n * self._inc

        if self.n > 0:
            k = self.n
            otherDay = other.weekday()
            if otherDay != self.weekday:
                other = other + timedelta((self.weekday - otherDay) % 7)
                k = k - 1
            other = other
            for i in range(k):
                other = other + self._inc
        else:
            k = self.n
            otherDay = other.weekday()
            if otherDay != self.weekday:
                other = other + timedelta((self.weekday - otherDay) % 7)
            for i in range(-k):
                other = other - self._inc

        other = datetime(other.year, other.month, other.day,
                         base.hour, base.minute, base.second, base.microsecond)
        return other

    @apply_index_wraps
    def apply_index(self, i):
        if self.weekday is None:
            return (i.to_period('W') + self.n).to_timestamp() + i.to_perioddelta('W')
        else:
            return self._end_apply_index(i, self.freqstr)

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        return dt.weekday() == self.weekday

    _prefix = 'W'

    @property
    def rule_code(self):
        suffix = ''
        if self.weekday is not None:
            suffix = '-%s' % (_int_to_weekday[self.weekday])
        return self._prefix + suffix

    @classmethod
    def _from_name(cls, suffix=None):
        if not suffix:
            weekday = None
        else:
            weekday = _weekday_to_int[suffix]
        return cls(weekday=weekday)

class WeekDay(object):
    MON = 0
    TUE = 1
    WED = 2
    THU = 3
    FRI = 4
    SAT = 5
    SUN = 6

_int_to_weekday = {
    WeekDay.MON: 'MON',
    WeekDay.TUE: 'TUE',
    WeekDay.WED: 'WED',
    WeekDay.THU: 'THU',
    WeekDay.FRI: 'FRI',
    WeekDay.SAT: 'SAT',
    WeekDay.SUN: 'SUN'
}

_weekday_to_int = dict((v, k) for k, v in _int_to_weekday.items())


class WeekOfMonth(DateOffset):
    """
    Describes monthly dates like "the Tuesday of the 2nd week of each month"

    Parameters
    ----------
    n : int
    week : {0, 1, 2, 3, ...}
        0 is 1st week of month, 1 2nd week, etc.
    weekday : {0, 1, ..., 6}
        0: Mondays
        1: Tuesdays
        2: Wednesdays
        3: Thursdays
        4: Fridays
        5: Saturdays
        6: Sundays
    """

    _adjust_dst = True

    def __init__(self, n=1, normalize=False, **kwds):
        self.n = n
        self.normalize = normalize
        self.weekday = kwds['weekday']
        self.week = kwds['week']

        if self.n == 0:
            raise ValueError('N cannot be 0')

        if self.weekday < 0 or self.weekday > 6:
            raise ValueError('Day must be 0<=day<=6, got %d' %
                             self.weekday)
        if self.week < 0 or self.week > 3:
            raise ValueError('Week must be 0<=day<=3, got %d' %
                             self.week)

        self.kwds = kwds

    @apply_wraps
    def apply(self, other):
        base = other
        offsetOfMonth = self.getOffsetOfMonth(other)

        if offsetOfMonth > other:
            if self.n > 0:
                months = self.n - 1
            else:
                months = self.n
        elif offsetOfMonth == other:
            months = self.n
        else:
            if self.n > 0:
                months = self.n
            else:
                months = self.n + 1

        other = self.getOffsetOfMonth(other + relativedelta(months=months, day=1))
        other = datetime(other.year, other.month, other.day, base.hour,
                         base.minute, base.second, base.microsecond)
        return other

    def getOffsetOfMonth(self, dt):
        w = Week(weekday=self.weekday)
        d = datetime(dt.year, dt.month, 1, tzinfo=dt.tzinfo)
        d = w.rollforward(d)

        for i in range(self.week):
            d = w.apply(d)

        return d

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        d = datetime(dt.year, dt.month, dt.day, tzinfo=dt.tzinfo)
        return d == self.getOffsetOfMonth(dt)

    @property
    def rule_code(self):
        return '%s-%d%s' % (self._prefix, self.week + 1,
                            _int_to_weekday.get(self.weekday, ''))

    _prefix = 'WOM'

    @classmethod
    def _from_name(cls, suffix=None):
        if not suffix:
            raise ValueError("Prefix %r requires a suffix." % (cls._prefix))
        # TODO: handle n here...
        # only one digit weeks (1 --> week 0, 2 --> week 1, etc.)
        week = int(suffix[0]) - 1
        weekday = _weekday_to_int[suffix[1:]]
        return cls(week=week, weekday=weekday)

class LastWeekOfMonth(DateOffset):
    """
    Describes monthly dates in last week of month like "the last Tuesday of each month"

    Parameters
    ----------
    n : int
    weekday : {0, 1, ..., 6}
        0: Mondays
        1: Tuesdays
        2: Wednesdays
        3: Thursdays
        4: Fridays
        5: Saturdays
        6: Sundays
    """
    def __init__(self, n=1, normalize=False, **kwds):
        self.n = n
        self.normalize = normalize
        self.weekday = kwds['weekday']

        if self.n == 0:
            raise ValueError('N cannot be 0')

        if self.weekday < 0 or self.weekday > 6:
            raise ValueError('Day must be 0<=day<=6, got %d' %
                            self.weekday)

        self.kwds = kwds

    @apply_wraps
    def apply(self, other):
        offsetOfMonth = self.getOffsetOfMonth(other)

        if offsetOfMonth > other:
            if self.n > 0:
                months = self.n - 1
            else:
                months = self.n
        elif offsetOfMonth == other:
            months = self.n
        else:
            if self.n > 0:
                months = self.n
            else:
                months = self.n + 1

        return self.getOffsetOfMonth(other + relativedelta(months=months, day=1))

    def getOffsetOfMonth(self, dt):
        m =  MonthEnd()
        d = datetime(dt.year, dt.month, 1, dt.hour, dt.minute,
                     dt.second, dt.microsecond, tzinfo=dt.tzinfo)
        eom = m.rollforward(d)
        w = Week(weekday=self.weekday)
        return w.rollback(eom)

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        return dt == self.getOffsetOfMonth(dt)

    @property
    def rule_code(self):
        return '%s-%s' % (self._prefix, _int_to_weekday.get(self.weekday, ''))

    _prefix = 'LWOM'

    @classmethod
    def _from_name(cls, suffix=None):
        if not suffix:
            raise ValueError("Prefix %r requires a suffix." % (cls._prefix))
        # TODO: handle n here...
        weekday = _weekday_to_int[suffix]
        return cls(weekday=weekday)


class QuarterOffset(DateOffset):
    """Quarter representation - doesn't call super"""

    #: default month for __init__
    _default_startingMonth = None
    #: default month in _from_name
    _from_name_startingMonth = None
    _adjust_dst = True
    # TODO: Consider combining QuarterOffset and YearOffset __init__ at some
    #       point
    def __init__(self, n=1, normalize=False, **kwds):
        self.n = n
        self.normalize = normalize
        self.startingMonth = kwds.get('startingMonth',
                                      self._default_startingMonth)

        self.kwds = kwds

    def isAnchored(self):
        return (self.n == 1 and self.startingMonth is not None)

    @classmethod
    def _from_name(cls, suffix=None):
        kwargs = {}
        if suffix:
            kwargs['startingMonth'] = _month_to_int[suffix]
        else:
            if cls._from_name_startingMonth is not None:
                kwargs['startingMonth'] = cls._from_name_startingMonth
        return cls(**kwargs)

    @property
    def rule_code(self):
        return '%s-%s' % (self._prefix, _int_to_month[self.startingMonth])


class BQuarterEnd(QuarterOffset):
    """DateOffset increments between business Quarter dates
    startingMonth = 1 corresponds to dates like 1/31/2007, 4/30/2007, ...
    startingMonth = 2 corresponds to dates like 2/28/2007, 5/31/2007, ...
    startingMonth = 3 corresponds to dates like 3/30/2007, 6/29/2007, ...
    """
    _outputName = 'BusinessQuarterEnd'
    _default_startingMonth = 3
    # 'BQ'
    _from_name_startingMonth = 12
    _prefix = 'BQ'

    @apply_wraps
    def apply(self, other):
        n = self.n
        base = other
        other = datetime(other.year, other.month, other.day,
                         other.hour, other.minute, other.second,
                         other.microsecond)

        wkday, days_in_month = tslib.monthrange(other.year, other.month)
        lastBDay = days_in_month - max(((wkday + days_in_month - 1)
                                        % 7) - 4, 0)

        monthsToGo = 3 - ((other.month - self.startingMonth) % 3)
        if monthsToGo == 3:
            monthsToGo = 0

        if n > 0 and not (other.day >= lastBDay and monthsToGo == 0):
            n = n - 1
        elif n <= 0 and other.day > lastBDay and monthsToGo == 0:
            n = n + 1

        other = other + relativedelta(months=monthsToGo + 3 * n, day=31)
        other = tslib._localize_pydatetime(other, base.tzinfo)
        if other.weekday() > 4:
            other = other - BDay()
        return other

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        modMonth = (dt.month - self.startingMonth) % 3
        return BMonthEnd().onOffset(dt) and modMonth == 0

_int_to_month = tslib._MONTH_ALIASES
_month_to_int = dict((v, k) for k, v in _int_to_month.items())


# TODO: This is basically the same as BQuarterEnd
class BQuarterBegin(QuarterOffset):
    _outputName = "BusinessQuarterBegin"
    # I suspect this is wrong for *all* of them.
    _default_startingMonth = 3
    _from_name_startingMonth = 1
    _prefix = 'BQS'

    @apply_wraps
    def apply(self, other):
        n = self.n
        wkday, _ = tslib.monthrange(other.year, other.month)

        first = _get_firstbday(wkday)

        monthsSince = (other.month - self.startingMonth) % 3

        if n <= 0 and monthsSince != 0:  # make sure to roll forward so negate
            monthsSince = monthsSince - 3

        # roll forward if on same month later than first bday
        if n <= 0 and (monthsSince == 0 and other.day > first):
            n = n + 1
        # pretend to roll back if on same month but before firstbday
        elif n > 0 and (monthsSince == 0 and other.day < first):
            n = n - 1

        # get the first bday for result
        other = other + relativedelta(months=3 * n - monthsSince)
        wkday, _ = tslib.monthrange(other.year, other.month)
        first = _get_firstbday(wkday)
        result = datetime(other.year, other.month, first,
                          other.hour, other.minute, other.second,
                          other.microsecond)
        return result


class QuarterEnd(QuarterOffset):
    """DateOffset increments between business Quarter dates
    startingMonth = 1 corresponds to dates like 1/31/2007, 4/30/2007, ...
    startingMonth = 2 corresponds to dates like 2/28/2007, 5/31/2007, ...
    startingMonth = 3 corresponds to dates like 3/31/2007, 6/30/2007, ...
    """
    _outputName = 'QuarterEnd'
    _default_startingMonth = 3
    _prefix = 'Q'

    def __init__(self, n=1, normalize=False, **kwds):
        self.n = n
        self.normalize = normalize
        self.startingMonth = kwds.get('startingMonth', 3)

        self.kwds = kwds

    def isAnchored(self):
        return (self.n == 1 and self.startingMonth is not None)

    @apply_wraps
    def apply(self, other):
        n = self.n
        other = datetime(other.year, other.month, other.day,
                         other.hour, other.minute, other.second,
                         other.microsecond)
        wkday, days_in_month = tslib.monthrange(other.year, other.month)

        monthsToGo = 3 - ((other.month - self.startingMonth) % 3)
        if monthsToGo == 3:
            monthsToGo = 0

        if n > 0 and not (other.day >= days_in_month and monthsToGo == 0):
            n = n - 1

        other = other + relativedelta(months=monthsToGo + 3 * n, day=31)
        return other

    @apply_index_wraps
    def apply_index(self, i):
        return self._end_apply_index(i, self.freqstr)

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        modMonth = (dt.month - self.startingMonth) % 3
        return MonthEnd().onOffset(dt) and modMonth == 0


class QuarterBegin(QuarterOffset):
    _outputName = 'QuarterBegin'
    _default_startingMonth = 3
    _from_name_startingMonth = 1
    _prefix = 'QS'

    def isAnchored(self):
        return (self.n == 1 and self.startingMonth is not None)

    @apply_wraps
    def apply(self, other):
        n = self.n
        wkday, days_in_month = tslib.monthrange(other.year, other.month)

        monthsSince = (other.month - self.startingMonth) % 3

        if n <= 0 and monthsSince != 0:
            # make sure you roll forward, so negate
            monthsSince = monthsSince - 3

        if n < 0 and (monthsSince == 0 and other.day > 1):
            # after start, so come back an extra period as if rolled forward
            n = n + 1

        other = other + relativedelta(months=3 * n - monthsSince, day=1)
        return other

    @apply_index_wraps
    def apply_index(self, i):
        freq_month = 12 if self.startingMonth == 1 else self.startingMonth - 1
        freqstr =  'Q-%s' % (_int_to_month[freq_month],)
        return self._beg_apply_index(i, freqstr)

class YearOffset(DateOffset):
    """DateOffset that just needs a month"""
    _adjust_dst = True
    def __init__(self, n=1, normalize=False, **kwds):
        self.month = kwds.get('month', self._default_month)

        if self.month < 1 or self.month > 12:
            raise ValueError('Month must go from 1 to 12')

        DateOffset.__init__(self, n=n, normalize=normalize, **kwds)

    @classmethod
    def _from_name(cls, suffix=None):
        kwargs = {}
        if suffix:
            kwargs['month'] = _month_to_int[suffix]
        return cls(**kwargs)

    @property
    def rule_code(self):
        return '%s-%s' % (self._prefix, _int_to_month[self.month])


class BYearEnd(YearOffset):
    """DateOffset increments between business EOM dates"""
    _outputName = 'BusinessYearEnd'
    _default_month = 12
    _prefix = 'BA'

    @apply_wraps
    def apply(self, other):
        n = self.n
        wkday, days_in_month = tslib.monthrange(other.year, self.month)
        lastBDay = (days_in_month -
                    max(((wkday + days_in_month - 1) % 7) - 4, 0))

        years = n
        if n > 0:
            if (other.month < self.month or
                    (other.month == self.month and other.day < lastBDay)):
                years -= 1
        elif n <= 0:
            if (other.month > self.month or
                    (other.month == self.month and other.day > lastBDay)):
                years += 1

        other = other + relativedelta(years=years)

        _, days_in_month = tslib.monthrange(other.year, self.month)
        result = datetime(other.year, self.month, days_in_month,
                          other.hour, other.minute, other.second,
                          other.microsecond)

        if result.weekday() > 4:
            result = result - BDay()

        return result


class BYearBegin(YearOffset):
    """DateOffset increments between business year begin dates"""
    _outputName = 'BusinessYearBegin'
    _default_month = 1
    _prefix = 'BAS'

    @apply_wraps
    def apply(self, other):
        n = self.n
        wkday, days_in_month = tslib.monthrange(other.year, self.month)

        first = _get_firstbday(wkday)

        years = n

        if n > 0:  # roll back first for positive n
            if (other.month < self.month or
                    (other.month == self.month and other.day < first)):
                years -= 1
        elif n <= 0:  # roll forward
            if (other.month > self.month or
                    (other.month == self.month and other.day > first)):
                years += 1

        # set first bday for result
        other = other + relativedelta(years=years)
        wkday, days_in_month = tslib.monthrange(other.year, self.month)
        first = _get_firstbday(wkday)
        return datetime(other.year, self.month, first, other.hour,
                        other.minute, other.second, other.microsecond)


class YearEnd(YearOffset):
    """DateOffset increments between calendar year ends"""
    _default_month = 12
    _prefix = 'A'

    @apply_wraps
    def apply(self, other):
        def _increment(date):
            if date.month == self.month:
                _, days_in_month = tslib.monthrange(date.year, self.month)
                if date.day != days_in_month:
                    year = date.year
                else:
                    year = date.year + 1
            elif date.month < self.month:
                year = date.year
            else:
                year = date.year + 1
            _, days_in_month = tslib.monthrange(year, self.month)
            return datetime(year, self.month, days_in_month,
                            date.hour, date.minute, date.second,
                            date.microsecond)

        def _decrement(date):
            year = date.year if date.month > self.month else date.year - 1
            _, days_in_month = tslib.monthrange(year, self.month)
            return datetime(year, self.month, days_in_month,
                            date.hour, date.minute, date.second,
                            date.microsecond)

        def _rollf(date):
            if date.month != self.month or\
               date.day < tslib.monthrange(date.year, date.month)[1]:
                date = _increment(date)
            return date

        n = self.n
        result = other
        if n > 0:
            while n > 0:
                result = _increment(result)
                n -= 1
        elif n < 0:
            while n < 0:
                result = _decrement(result)
                n += 1
        else:
            # n == 0, roll forward
            result = _rollf(result)
        return result

    @apply_index_wraps
    def apply_index(self, i):
        # convert month anchor to annual period tuple
        return self._end_apply_index(i, self.freqstr)

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        wkday, days_in_month = tslib.monthrange(dt.year, self.month)
        return self.month == dt.month and dt.day == days_in_month


class YearBegin(YearOffset):
    """DateOffset increments between calendar year begin dates"""
    _default_month = 1
    _prefix = 'AS'

    @apply_wraps
    def apply(self, other):
        def _increment(date, n):
            year = date.year + n - 1
            if date.month >= self.month:
                year += 1
            return datetime(year, self.month, 1, date.hour, date.minute,
                            date.second, date.microsecond)

        def _decrement(date, n):
            year = date.year + n + 1
            if date.month < self.month or (date.month == self.month and
                                           date.day == 1):
                year -= 1
            return datetime(year, self.month, 1, date.hour, date.minute,
                            date.second, date.microsecond)

        def _rollf(date):
            if (date.month != self.month) or date.day > 1:
                date = _increment(date, 1)
            return date

        n = self.n
        result = other
        if n > 0:
            result = _increment(result, n)
        elif n < 0:
            result = _decrement(result, n)
        else:
            # n == 0, roll forward
            result = _rollf(result)
        return result

    @apply_index_wraps
    def apply_index(self, i):
        freq_month = 12 if self.month == 1 else self.month - 1
        freqstr =  'A-%s' % (_int_to_month[freq_month],)
        return self._beg_apply_index(i, freqstr)

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        return dt.month == self.month and dt.day == 1


class FY5253(DateOffset):
    """
    Describes 52-53 week fiscal year. This is also known as a 4-4-5 calendar.

    It is used by companies that desire that their
    fiscal year always end on the same day of the week.

    It is a method of managing accounting periods.
    It is a common calendar structure for some industries,
    such as retail, manufacturing and parking industry.

    For more information see:
    http://en.wikipedia.org/wiki/4%E2%80%934%E2%80%935_calendar


    The year may either:
    - end on the last X day of the Y month.
    - end on the last X day closest to the last day of the Y month.

    X is a specific day of the week.
    Y is a certain month of the year

    Parameters
    ----------
    n : int
    weekday : {0, 1, ..., 6}
        0: Mondays
        1: Tuesdays
        2: Wednesdays
        3: Thursdays
        4: Fridays
        5: Saturdays
        6: Sundays
    startingMonth : The month in which fiscal years end. {1, 2, ... 12}
    variation : str
        {"nearest", "last"} for "LastOfMonth" or "NearestEndMonth"
    """

    _prefix = 'RE'
    _suffix_prefix_last = 'L'
    _suffix_prefix_nearest = 'N'
    _adjust_dst = True

    def __init__(self, n=1, normalize=False, **kwds):
        self.n = n
        self.normalize = normalize
        self.startingMonth = kwds['startingMonth']
        self.weekday = kwds["weekday"]

        self.variation = kwds["variation"]

        self.kwds = kwds

        if self.n == 0:
            raise ValueError('N cannot be 0')

        if self.variation not in ["nearest", "last"]:
            raise ValueError('%s is not a valid variation' % self.variation)

        if self.variation == "nearest":
            weekday_offset = weekday(self.weekday)
            self._rd_forward = relativedelta(weekday=weekday_offset)
            self._rd_backward = relativedelta(weekday=weekday_offset(-1))
        else:
            self._offset_lwom = LastWeekOfMonth(n=1, weekday=self.weekday)

    def isAnchored(self):
        return self.n == 1 \
                and self.startingMonth is not None \
                and self.weekday is not None

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        dt = datetime(dt.year, dt.month, dt.day)
        year_end = self.get_year_end(dt)

        if self.variation == "nearest":
            # We have to check the year end of "this" cal year AND the previous
            return year_end == dt or \
                self.get_year_end(dt - relativedelta(months=1)) == dt
        else:
            return year_end == dt

    @apply_wraps
    def apply(self, other):
        n = self.n
        prev_year = self.get_year_end(
                        datetime(other.year - 1, self.startingMonth, 1))
        cur_year = self.get_year_end(
                        datetime(other.year, self.startingMonth, 1))
        next_year = self.get_year_end(
                        datetime(other.year + 1, self.startingMonth, 1))
        prev_year = tslib._localize_pydatetime(prev_year, other.tzinfo)
        cur_year = tslib._localize_pydatetime(cur_year, other.tzinfo)
        next_year = tslib._localize_pydatetime(next_year, other.tzinfo)

        if n > 0:
            if other == prev_year:
                year = other.year - 1
            elif other == cur_year:
                year = other.year
            elif other == next_year:
                year = other.year + 1
            elif other < prev_year:
                year = other.year - 1
                n -= 1
            elif other < cur_year:
                year = other.year
                n -= 1
            elif other < next_year:
                year = other.year + 1
                n -= 1
            else:
                assert False

            result = self.get_year_end(datetime(year + n, self.startingMonth, 1))

            result = datetime(result.year, result.month, result.day,
                              other.hour, other.minute, other.second, other.microsecond)
            return result
        else:
            n = -n
            if other == prev_year:
                year = other.year - 1
            elif other == cur_year:
                year = other.year
            elif other == next_year:
                year = other.year + 1
            elif other > next_year:
                year = other.year + 1
                n -= 1
            elif other > cur_year:
                year = other.year
                n -= 1
            elif other > prev_year:
                year = other.year - 1
                n -= 1
            else:
                assert False

            result = self.get_year_end(datetime(year - n, self.startingMonth, 1))

            result = datetime(result.year, result.month, result.day,
                              other.hour, other.minute, other.second, other.microsecond)
            return result

    def get_year_end(self, dt):
        if self.variation == "nearest":
            return self._get_year_end_nearest(dt)
        else:
            return self._get_year_end_last(dt)

    def get_target_month_end(self, dt):
        target_month = datetime(dt.year, self.startingMonth, 1, tzinfo=dt.tzinfo)
        next_month_first_of = target_month + relativedelta(months=+1)
        return next_month_first_of + relativedelta(days=-1)

    def _get_year_end_nearest(self, dt):
        target_date = self.get_target_month_end(dt)
        if target_date.weekday() == self.weekday:
            return target_date
        else:
            forward = target_date + self._rd_forward
            backward = target_date + self._rd_backward

            if forward - target_date < target_date - backward:
                return forward
            else:
                return backward

    def _get_year_end_last(self, dt):
        current_year = datetime(dt.year, self.startingMonth, 1, tzinfo=dt.tzinfo)
        return current_year + self._offset_lwom

    @property
    def rule_code(self):
        suffix = self.get_rule_code_suffix()
        return "%s-%s" % (self._get_prefix(), suffix)

    def _get_prefix(self):
        return self._prefix

    def _get_suffix_prefix(self):
        if self.variation == "nearest":
            return self._suffix_prefix_nearest
        else:
            return self._suffix_prefix_last

    def get_rule_code_suffix(self):
        return '%s-%s-%s' % (self._get_suffix_prefix(), \
                           _int_to_month[self.startingMonth], \
                         _int_to_weekday[self.weekday])

    @classmethod
    def _parse_suffix(cls, varion_code, startingMonth_code, weekday_code):
        if varion_code == "N":
            variation = "nearest"
        elif varion_code == "L":
            variation = "last"
        else:
            raise ValueError(
                "Unable to parse varion_code: %s" % (varion_code,))

        startingMonth = _month_to_int[startingMonth_code]
        weekday = _weekday_to_int[weekday_code]

        return {
                "weekday": weekday,
                "startingMonth": startingMonth,
                "variation": variation,
                }

    @classmethod
    def _from_name(cls, *args):
        return cls(**cls._parse_suffix(*args))


class FY5253Quarter(DateOffset):
    """
    DateOffset increments between business quarter dates
    for 52-53 week fiscal year (also known as a 4-4-5 calendar).

    It is used by companies that desire that their
    fiscal year always end on the same day of the week.

    It is a method of managing accounting periods.
    It is a common calendar structure for some industries,
    such as retail, manufacturing and parking industry.

    For more information see:
    http://en.wikipedia.org/wiki/4%E2%80%934%E2%80%935_calendar

    The year may either:
    - end on the last X day of the Y month.
    - end on the last X day closest to the last day of the Y month.

    X is a specific day of the week.
    Y is a certain month of the year

    startingMonth = 1 corresponds to dates like 1/31/2007, 4/30/2007, ...
    startingMonth = 2 corresponds to dates like 2/28/2007, 5/31/2007, ...
    startingMonth = 3 corresponds to dates like 3/30/2007, 6/29/2007, ...

    Parameters
    ----------
    n : int
    weekday : {0, 1, ..., 6}
        0: Mondays
        1: Tuesdays
        2: Wednesdays
        3: Thursdays
        4: Fridays
        5: Saturdays
        6: Sundays
    startingMonth : The month in which fiscal years end. {1, 2, ... 12}
    qtr_with_extra_week : The quarter number that has the leap
        or 14 week when needed. {1,2,3,4}
    variation : str
        {"nearest", "last"} for "LastOfMonth" or "NearestEndMonth"
    """

    _prefix = 'REQ'
    _adjust_dst = True

    def __init__(self, n=1, normalize=False, **kwds):
        self.n = n
        self.normalize = normalize

        self.qtr_with_extra_week = kwds["qtr_with_extra_week"]

        self.kwds = kwds

        if self.n == 0:
            raise ValueError('N cannot be 0')

        self._offset = FY5253( \
                            startingMonth=kwds['startingMonth'], \
                            weekday=kwds["weekday"],
                            variation=kwds["variation"])

    def isAnchored(self):
        return self.n == 1 and self._offset.isAnchored()

    @apply_wraps
    def apply(self, other):
        base = other
        n = self.n

        if n > 0:
            while n > 0:
                if not self._offset.onOffset(other):
                    qtr_lens = self.get_weeks(other)
                    start = other - self._offset
                else:
                    start = other
                    qtr_lens = self.get_weeks(other + self._offset)

                for weeks in qtr_lens:
                    start += relativedelta(weeks=weeks)
                    if start > other:
                        other = start
                        n -= 1
                        break

        else:
            n = -n
            while n > 0:
                if not self._offset.onOffset(other):
                    qtr_lens = self.get_weeks(other)
                    end = other + self._offset
                else:
                    end = other
                    qtr_lens = self.get_weeks(other)

                for weeks in reversed(qtr_lens):
                    end -= relativedelta(weeks=weeks)
                    if end < other:
                        other = end
                        n -= 1
                        break
        other = datetime(other.year, other.month, other.day,
                         base.hour, base.minute, base.second, base.microsecond)
        return other

    def get_weeks(self, dt):
        ret = [13] * 4

        year_has_extra_week = self.year_has_extra_week(dt)

        if year_has_extra_week:
            ret[self.qtr_with_extra_week - 1] = 14

        return ret

    def year_has_extra_week(self, dt):
        if self._offset.onOffset(dt):
            prev_year_end = dt - self._offset
            next_year_end = dt
        else:
            next_year_end = dt + self._offset
            prev_year_end = dt - self._offset

        week_in_year = (next_year_end - prev_year_end).days / 7

        return week_in_year == 53

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        if self._offset.onOffset(dt):
            return True

        next_year_end = dt - self._offset

        qtr_lens = self.get_weeks(dt)

        current = next_year_end
        for qtr_len in qtr_lens[0:4]:
            current += relativedelta(weeks=qtr_len)
            if dt == current:
                return True
        return False

    @property
    def rule_code(self):
        suffix = self._offset.get_rule_code_suffix()
        return "%s-%s" % (self._prefix,
                          "%s-%d" % (suffix, self.qtr_with_extra_week))

    @classmethod
    def _from_name(cls, *args):
        return cls(**dict(FY5253._parse_suffix(*args[:-1]),
                          qtr_with_extra_week=int(args[-1])))

class Easter(DateOffset):
    '''
    DateOffset for the Easter holiday using
    logic defined in dateutil.  Right now uses
    the revised method which is valid in years
    1583-4099.
    '''
    _adjust_dst = True

    def __init__(self, n=1, **kwds):
        super(Easter, self).__init__(n, **kwds)

    @apply_wraps
    def apply(self, other):
        currentEaster = easter(other.year)
        currentEaster = datetime(currentEaster.year, currentEaster.month, currentEaster.day)
        currentEaster = tslib._localize_pydatetime(currentEaster, other.tzinfo)

        # NOTE: easter returns a datetime.date so we have to convert to type of other
        if self.n >= 0:
            if other >= currentEaster:
                new = easter(other.year + self.n)
            else:
                new = easter(other.year + self.n - 1)
        else:
            if other > currentEaster:
                new = easter(other.year + self.n + 1)
            else:
                new = easter(other.year + self.n)

        new = datetime(new.year, new.month, new.day, other.hour,
                       other.minute, other.second, other.microsecond)
        return new

    def onOffset(self, dt):
        if self.normalize and not _is_normalized(dt):
            return False
        return date(dt.year, dt.month, dt.day) == easter(dt.year)

#----------------------------------------------------------------------
# Ticks

import operator


def _tick_comp(op):
    def f(self, other):
        return op(self.delta, other.delta)

    return f


class Tick(SingleConstructorOffset):
    _inc = Timedelta(microseconds=1000)

    __gt__ = _tick_comp(operator.gt)
    __ge__ = _tick_comp(operator.ge)
    __lt__ = _tick_comp(operator.lt)
    __le__ = _tick_comp(operator.le)
    __eq__ = _tick_comp(operator.eq)
    __ne__ = _tick_comp(operator.ne)

    def __add__(self, other):
        if isinstance(other, Tick):
            if type(self) == type(other):
                return type(self)(self.n + other.n)
            else:
                return _delta_to_tick(self.delta + other.delta)
        try:
            return self.apply(other)
        except ApplyTypeError:
            return NotImplemented

    def __eq__(self, other):
        if isinstance(other, compat.string_types):
            from pandas.tseries.frequencies import to_offset

            other = to_offset(other)

        if isinstance(other, Tick):
            return self.delta == other.delta
        else:
            return DateOffset.__eq__(self, other)

    # This is identical to DateOffset.__hash__, but has to be redefined here
    # for Python 3, because we've redefined __eq__.
    def __hash__(self):
        return hash(self._params())

    def __ne__(self, other):
        if isinstance(other, compat.string_types):
            from pandas.tseries.frequencies import to_offset

            other = to_offset(other)

        if isinstance(other, Tick):
            return self.delta != other.delta
        else:
            return DateOffset.__ne__(self, other)

    @property
    def delta(self):
        return self.n * self._inc

    @property
    def nanos(self):
        return _delta_to_nanoseconds(self.delta)

    def apply(self, other):
        # Timestamp can handle tz and nano sec, thus no need to use apply_wraps
        if isinstance(other, (datetime, np.datetime64, date)):
            return as_timestamp(other) + self
        if isinstance(other, timedelta):
            return other + self.delta
        elif isinstance(other, type(self)):
            return type(self)(self.n + other.n)
        else:
            raise ApplyTypeError('Unhandled type: %s' % type(other).__name__)

    _prefix = 'undefined'


    def isAnchored(self):
        return False


def _delta_to_tick(delta):
    if delta.microseconds == 0:
        if delta.seconds == 0:
            return Day(delta.days)
        else:
            seconds = delta.days * 86400 + delta.seconds
            if seconds % 3600 == 0:
                return Hour(seconds / 3600)
            elif seconds % 60 == 0:
                return Minute(seconds / 60)
            else:
                return Second(seconds)
    else:
        nanos = _delta_to_nanoseconds(delta)
        if nanos % 1000000 == 0:
            return Milli(nanos // 1000000)
        elif nanos % 1000 == 0:
            return Micro(nanos // 1000)
        else:  # pragma: no cover
            return Nano(nanos)

_delta_to_nanoseconds = tslib._delta_to_nanoseconds


class Day(Tick):
    _inc = Timedelta(days=1)
    _prefix = 'D'


class Hour(Tick):
    _inc = Timedelta(hours=1)
    _prefix = 'H'


class Minute(Tick):
    _inc = Timedelta(minutes=1)
    _prefix = 'T'


class Second(Tick):
    _inc = Timedelta(seconds=1)
    _prefix = 'S'


class Milli(Tick):
    _inc = Timedelta(milliseconds=1)
    _prefix = 'L'


class Micro(Tick):
    _inc = Timedelta(microseconds=1)
    _prefix = 'U'


class Nano(Tick):
    _inc = Timedelta(nanoseconds=1)
    _prefix = 'N'


BDay = BusinessDay
BMonthEnd = BusinessMonthEnd
BMonthBegin = BusinessMonthBegin
CBMonthEnd = CustomBusinessMonthEnd
CBMonthBegin = CustomBusinessMonthBegin
CDay = CustomBusinessDay


def _get_firstbday(wkday):
    """
    wkday is the result of monthrange(year, month)

    If it's a saturday or sunday, increment first business day to reflect this
    """
    first = 1
    if wkday == 5:  # on Saturday
        first = 3
    elif wkday == 6:  # on Sunday
        first = 2
    return first


def generate_range(start=None, end=None, periods=None,
                   offset=BDay(), time_rule=None):
    """
    Generates a sequence of dates corresponding to the specified time
    offset. Similar to dateutil.rrule except uses pandas DateOffset
    objects to represent time increments

    Parameters
    ----------
    start : datetime (default None)
    end : datetime (default None)
    periods : int, optional
    time_rule : (legacy) name of DateOffset object to be used, optional
        Corresponds with names expected by tseries.frequencies.get_offset

    Notes
    -----
    * This method is faster for generating weekdays than dateutil.rrule
    * At least two of (start, end, periods) must be specified.
    * If both start and end are specified, the returned dates will
    satisfy start <= date <= end.
    * If both time_rule and offset are specified, time_rule supersedes offset.

    Returns
    -------
    dates : generator object

    """
    if time_rule is not None:
        from pandas.tseries.frequencies import get_offset

        offset = get_offset(time_rule)

    start = to_datetime(start)
    end = to_datetime(end)

    if start and not offset.onOffset(start):
        start = offset.rollforward(start)

    elif end and not offset.onOffset(end):
        end = offset.rollback(end)

    if periods is None and end < start:
        end = None
        periods = 0

    if end is None:
        end = start + (periods - 1) * offset

    if start is None:
        start = end - (periods - 1) * offset

    cur = start
    if offset.n >= 0:
        while cur <= end:
            yield cur

            # faster than cur + offset
            next_date = offset.apply(cur)
            if next_date <= cur:
                raise ValueError('Offset %s did not increment date' % offset)
            cur = next_date
    else:
        while cur >= end:
            yield cur

            # faster than cur + offset
            next_date = offset.apply(cur)
            if next_date >= cur:
                raise ValueError('Offset %s did not decrement date' % offset)
            cur = next_date

prefix_mapping = dict((offset._prefix, offset) for offset in [
    YearBegin,                # 'AS'
    YearEnd,                  # 'A'
    BYearBegin,               # 'BAS'
    BYearEnd,                 # 'BA'
    BusinessDay,              # 'B'
    BusinessMonthBegin,       # 'BMS'
    BusinessMonthEnd,         # 'BM'
    BQuarterEnd,              # 'BQ'
    BQuarterBegin,            # 'BQS'
    BusinessHour,             # 'BH'
    CustomBusinessDay,        # 'C'
    CustomBusinessMonthEnd,   # 'CBM'
    CustomBusinessMonthBegin, # 'CBMS'
    MonthEnd,                 # 'M'
    MonthBegin,               # 'MS'
    Week,                     # 'W'
    Second,                   # 'S'
    Minute,                   # 'T'
    Micro,                    # 'U'
    QuarterEnd,               # 'Q'
    QuarterBegin,             # 'QS'
    Milli,                    # 'L'
    Hour,                     # 'H'
    Day,                      # 'D'
    WeekOfMonth,              # 'WOM'
    FY5253,
    FY5253Quarter,
])

prefix_mapping['N'] = Nano

def _make_offset(key):
    """Gets offset based on key. KeyError if prefix is bad, ValueError if
    suffix is bad. All handled by `get_offset` in tseries/frequencies. Not
    public."""
    if key is None:
        return None
    split = key.split('-')
    klass = prefix_mapping[split[0]]
    # handles case where there's no suffix (and will TypeError if too many '-')
    obj = klass._from_name(*split[1:])
    obj._named = key
    return obj
