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)
| x | a date-time object |
|---|---|
| value | a numeric object |
the years element of x as a decimal number
year does not yet support years before 0 C.E.
https://en.wikipedia.org/wiki/ISO_week_date
#> [1] 2012year(x) <- 2001 year(x) > 1995#> [1] TRUE