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.
year(x)
year(x) <- value
isoyear(x)
epiyear(x)
a date-time object
a numeric object
the years element of x as a decimal number
year does not yet support years before 0 C.E.
x <- ymd("2012-03-26")
year(x)
#> [1] 2012
year(x) <- 2001
year(x) > 1995
#> [1] TRUE