as.POSIXct gives an unexpected timezone

Question

I\'m trying to convert a yearmon date (from the zoo package) to a POSIXct in the UTC timezone. This is what I tried to do:

> as.POSIXct(as.yearmon(\"2010         


        

Answer 1

This seems to be an oddity with the date/time "POSIXct" class methods. Try formatting the "Date" or "yearmon" variable first so that as.POSIXct.character rather than as.POSIXct.{Date, yearmon} is dispatched:

Date

> d <- as.Date("2010-01-01")
> as.POSIXct(format(d), tz = "UTC")
[1] "2010-01-01 UTC"

yearmon

> library(zoo)
> y <- as.yearmon("2010-01")
> as.POSIXct(format(y, format = "%Y-%m-01"), tz = "UTC")
[1] "2010-01-01 UTC"
> # or
> as.POSIXct(format(as.Date(y)), tz = "UTC")
[1] "2010-01-01 UTC"