Get/set years component of a date-timeSource:
Date-time must be a POSIXct, POSIXlt, Date, Period or any other object convertible to POSIXlt.
isoyear() returns years according to the ISO 8601 week calendar.
epiyear() returns years according to the epidemilogical week calendars.
x <- ymd("2012-03-26") year(x) #>  2012 year(x) <- 2001 year(x) > 1995 #>  TRUE