Extract month and year from a zoo::yearmon object

Use the format() method for objects of class "yearmon". Here is your example date (properly created!)

date1 <- as.yearmon("Mar 2012", "%b %Y")

Then we can extract the date parts as required:

> format(date1, "%b") ## Month, char, abbreviated
[1] "Mar"
> format(date1, "%Y") ## Year with century
[1] "2012"
> format(date1, "%m") ## numeric month
[1] "03"

These are returned as characters. Where appropriate, wrap in as.numeric() if you want the year or numeric month as a numeric variable, e.g.

> as.numeric(format(date1, "%m"))
[1] 3
> as.numeric(format(date1, "%Y"))
[1] 2012

See ?yearmon and ?strftime for details – the latter explains the placeholder characters you can use.