Add a month to a Date

Question

I am trying to add a month to a date i have. But then its not possible in a straight manner so far. Following is what i tried.

d <- as.Date("2004-01-31")
d + 60
# [1] "2004-03-31"

Adding wont help as the month wont be overlapped.

seq(as.Date("2004-01-31"), by = "month", length = 2) 
# [1] "2004-01-31" "2004-03-02"

Above might work , but again its not straight forward. Also its also adding 30 days or something to the date which has issues like the below

seq(as.Date("2004-01-31"), by = "month", length = 10) 
#  [1] "2004-01-31" "2004-03-02" "2004-03-31" "2004-05-01" "2004-05-31" "2004-07-01" "2004-07-31" "2004-08-31" "2004-10-01" "2004-10-31"

In the above , for the first 2 dates , month haven’t changed.

Also the following approach also failed for month but was success for year

d <- as.POSIXlt(as.Date("2010-01-01"))
d$year <- d$year +1
d
# [1] "2011-01-01 UTC"
d <- as.POSIXlt(as.Date("2010-01-01"))
d$month <- d$month +1
d

Error in format.POSIXlt(x, usetz = TRUE) : invalid 'x' argument

What is the right method to do this ?

Answer 1

Function %m+% from lubridate adds one month without exceeding last day of the new month.

library(lubridate)
(d <- ymd("2012-01-31"))
 1 parsed with %Y-%m-%d
[1] "2012-01-31 UTC"
d %m+% months(1)
[1] "2012-02-29 UTC"