Question: Are there any built on functions that can be used on a data frame object to generate variables on a class `Date` time series to create day of the Week, Month, Year, Week of the Year, etc in R?

The `weekdays`, `months`, `quarters`, functions in the base package generate text output, looking for numerical output to denote that 3/5/2012, for example, is a Friday, 3rd day of the month, 1 week of the month, and the 63 day of the year, etc.

Answer: 
You get a few of those just from `POSIXlt`, with its weird convention. Year needs to 1900,
month is on the 0 to 11 range -- but you do get weekday and day-of-the-year.

```
R> dd <- as.Date("2012-05-03")
R> as.POSIXlt(dd)
[1] "2012-05-03 UTC"

```

Then

```
R> unclass(as.POSIXlt(dd))
$sec
[1] 0

$min
[1] 0

$hour
[1] 0

$mday
[1] 3

$mon
[1] 4

$year
[1] 112

$wday
[1] 4

$yday
[1] 123

$isdst
[1] 0

attr(,"tzone")
[1] "UTC"
R> 

```
There are a couple of options that I can think of.

First, you could use the class `as.POSIXlt` so that you can subset with things like `df$date$yday`. The `as.POSIXlt()` includes the elements of dates as a list underneath that can be accessed that way. 

Also, the package `lubridate` has functions like 

```
yday(x)
wday(x)
mday(x)

```