R error: unknown timezone with as.POSIXct()

Question

I am trying to convert a unix epoch timestamps to a date-time object using as.POSIXct()

I need to specify timezones (either Europe/London or UTC) when I call as.POSI

Answer 1

It does look like you need to update your system with a timezone, even though it isn't being used.

I can't seem to set my timezone to NA, but if I set my environment with, for example Sys.setenv(TZ='Twilight Zone'), or anything that isn't on the tz list I also get the same errors that you do.

Answer 2

Looking at the output it is not actually giving a warning about 'Europe/London', just about other variations ('BST' and 'default/Europe/London').

Could it be that it are errors of previous commands still lingering? Do you get the same if run you the as.POSIXct(1445329330, tz="Europe/London", origin="1970-01-01") again, or even restart R?

I still get the error about BST even if using the correct timezone

> as.POSIXct(1445329330, tz="BST", origin="1970-01-01")
[1] "2015-10-20 08:22:10 GMT"
Warning message:
In as.POSIXlt.POSIXct(x, tz) : unknown timezone 'BST'
> as.POSIXct(1445329330, tz="Europe/London", origin="1970-01-01")
[1] "2015-10-20 09:22:10 BST"
Warning message:
In as.POSIXlt.POSIXct(x, tz) : unknown timezone 'BST'

Answer 3

I am having a similar issue on macOS High Sierra 10.13.1. As soon as, I try to do anything with dates, I get the following error.

> as.POSIXct("2017-10-01", format = "%Y-%m-%d")
[1] "2017-10-01 GMT"
Warning message:
In strptime(x, format, tz = tz) :
  unknown timezone 'zone/tz/2017c.1.0/zoneinfo/Pacific/Auckland'

The warning goes away if I set the environment variable to my timezone and I get the date back with the correct timezone.

> Sys.setenv(TZ = "Pacific/Auckland")
> as.POSIXct("2017-10-01")
[1] "2017-10-01 NZDT"

So, I have been setting the environment variable every time I need to do something to do with dates.

However, I have found this link talking about the same thing. Peter Dalgaard from R Core Team has replied saying this was a bug in macOS 10.13 Beta and that it is up to Apple to sort it out.

I am thinking to put Sys.setenv(TZ = "Pacific/Auckland") into .Rprofile so that it sets the time zone every time I start RStudio. I hope this helps.

Here is a link that might be useful if you want to try the .Rprofile approach I mentioned.

Update: It seems like this has been resolved in R 3.4.3. You can read more about it in the R news. Below is the related part of the release notes.

INSTALLATION on a UNIX-ALIKE

A workaround has been added for the changes in location of time-zone files in macOS 10.13 'High Sierra' and again in 10.13.1, so the default time zone is deduced correctly from the system setting when R is configured with --with-internal-tzcode (the default on macOS).

I can confirm that the new version of R resolves the issues with date/time objects.

> Sys.timezone()
[1] "Pacific/Auckland"
> Sys.time()
[1] "2017-12-30 16:22:32 NZDT"