ValueError: too many values to unpack (expected 3)
I want to calculate the days between two dates.

```
def isLeapYear(year):
    if year%400 == 0:
            return True
    elif year%100!=0 and year%4==0:
        return True
    else:
        return False

def nextDay(year,month,day):
    if isLeapYear(year):
        daysOfMonths1 = [ 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31] 
        daysOfMonths = daysOfMonths1
        return daysOfMonths
    else:
        daysOfMonths2 = [ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
        daysOfMonths = daysOfMonths2
        return daysOfMonths
    if day < daysOfMonths[month-1]:
        return year, month, day + 1
    else:
        if month == 12:
            return year + 1, 1, 1
        else:
            return year, month + 1, 1
        
def dateIsBefore(year1, month1, day1, year2, month2, day2):
    """Returns True if year1-month1-day1 is before year2-month2-day2. Otherwise, returns False."""
    if year1 < year2:
        return True
    if year1 == year2:
        if month1 < month2:
            return True
        if month1 == month2:
            return day1 < day2
    return False        

def daysBetweenDates(year1, month1, day1, year2, month2, day2):
    """Returns the number of days between year1/month1/day1
       and year2/month2/day2. Assumes inputs are valid dates
       in Gregorian calendar."""
    # program defensively! Add an assertion if the input is not valid!
    assert not dateIsBefore(year2, month2, day2, year1, month1, day1)
    days = 0
    while dateIsBefore(year1, month1, day1, year2, month2, day2):
        year1, month1, day1 = nextDay(year1, month1, day1)
        days += 1
    return days

    
print(daysBetweenDates(2012,1,1,2012,2,29))

```
Sadly this doesn't work:

`>>> runfile('G:/Anaconda3/ex1.py', wdir='G:/Anaconda3')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "G:\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 866, in runfile
    execfile(filename, namespace)
  File "G:\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 102, in execfile
    exec(compile(f.read(), filename, 'exec'), namespace)
  File "G:/Anaconda3/ex1.py", line 56, in <module>
    print(daysBetweenDates(2012,1,1,2012,2,22))
  File "G:/Anaconda3/ex1.py", line 51, in daysBetweenDates
    year1, month1, day1 = nextDay(year1, month1, day1)
ValueError: too many values to unpack (expected 3)`