AddMonths: Add a Month to a Date

AddMonthsR Documentation

Add a Month to a Date


Clueless adding numbers of months to a date will in some cases lead to invalid dates, think of e.g. 2012-01-30 + 1 month.
AddMonths ensures that the result is always a valid date, e.g. as.Date("2013-01-31") + 1 month will be "2013-02-28". If number n is negative, the months will be subtracted.


AddMonths(x, n, ...)



a Date object (or something which can be coerced by as.Date(x, ...) to such an object) to which a number of months has to be added.


the number of months to be added. If n is negative the months will be subtracted.


the dots are passed to as.Date, e.g. for supplying origin.


All parameters will be recyled if necessary.


a vector of class Date with the same dimension as x, containing the transformed dates.


Andri Signorell <>, based on code by Roland Rapold and Antonio


Thanks to Antonio:

See Also

AddMonthsYM; Date functions: Year, Month, etc.


# characters will be coerced to Date
AddMonths("2013-01-31", 1)

# negative n
AddMonths(as.Date("2013-03-31"), -1)

# Arguments will be recycled
# (with warning if the longer is not a multiple of length of shorter)
AddMonths(c("2013-01-31", "2013-03-31", "2013-10-31", "2013-12-31"), c(1,-1))

x <- as.POSIXct(c("2015-01-31", "2015-08-31"))
n <- c(1, 3)
AddMonths(x, n)

# mind the origin if x supplied as numeric ...
x <- as.numeric(as.Date(x))
AddMonths(x, n, origin=as.Date("1970-01-01"))

DescTools documentation built on Nov. 20, 2023, 5:08 p.m.