R SIG Debian - Apr 2020 - Timezone conversion on Ubuntu 20.04

Hi all,

I am testing R 4.0 and ran into an issue with timezones on Ubuntu
Focal: converting a timestamp to another timezone results in NA:

  as.POSIXct(as.POSIXlt(Sys.time(), tz = "CET"), tz = "EST")

This only happens on Ubuntu Focal, it seems to work fine on Ubuntu
Bionic. I am the standard ubuntu docker image icw/ r-base from Dirk's
ppa:edd/r-4.0 on both systems.

Am I missing a system dependency for tzone data?

Jeroen

On 4/24/20 4:02 PM, Jeroen Ooms wrote:
> Hi all,
>
> I am testing R 4.0 and ran into an issue with timezones on Ubuntu
> Focal: converting a timestamp to another timezone results in NA:
>
>    as.POSIXct(as.POSIXlt(Sys.time(), tz = "CET"), tz =
"EST")
>
> This only happens on Ubuntu Focal, it seems to work fine on Ubuntu
> Bionic. I am the standard ubuntu docker image icw/ r-base from Dirk's
> ppa:edd/r-4.0 on both systems.
>
> Am I missing a system dependency for tzone data?

I don't really know but I do know that "EST" is often not a
specific
valid value. It is used by both the USA and Australia. More valid 
designation would probably be "America/New_York"

The vector of valid names is returned by:

OlsonNames(tzdir = NULL)

-- 

David.
>
> Jeroen
>
> _______________________________________________
> R-SIG-Debian mailing list
> R-SIG-Debian at r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-debian

On 24 April 2020 at 17:46, David Winsemius wrote:
| On 4/24/20 4:02 PM, Jeroen Ooms wrote:
| > I am testing R 4.0 and ran into an issue with timezones on Ubuntu
| > Focal: converting a timestamp to another timezone results in NA:
| >
| >    as.POSIXct(as.POSIXlt(Sys.time(), tz = "CET"), tz =
"EST")
| >
| > This only happens on Ubuntu Focal, it seems to work fine on Ubuntu
| > Bionic. I am the standard ubuntu docker image icw/ r-base from Dirk's
| > ppa:edd/r-4.0 on both systems.
| >
| > Am I missing a system dependency for tzone data?

Maybe. What does `dpkg -s tzdata` say? Installed?  Or not?

The base images are pretty narrow and may simply not have it installed.
 
| I don't really know but I do know that "EST" is often not a
specific
| valid value. It is used by both the USA and Australia. More valid 
| designation would probably be "America/New_York"
| 
| The vector of valid names is returned by:
| 
| OlsonNames(tzdir = NULL)

Excellent point by David.

Also, there are _two_ issues here:

 - Does the machine itself have timezone information, ie can you access with
   anything other than R?  You hinted at that with question about
'tzdata'

 - If it does, did R regress?  At some point years ago R was less clever
   about finding tz info when the /etc/ softlink was not set. I coded up one
   smarter heuristic in CRAN package 'gettz'; later R itself carried
some of
   that same logic. This obviously needs the system info from the previous
   question.

Dirk

-- 
http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org

Am Samstag, 25. April 2020, 01:02:38 CEST schrieb Jeroen
Ooms:
> Hi all,
> 
> I am testing R 4.0 and ran into an issue with timezones on Ubuntu
> Focal: converting a timestamp to another timezone results in NA:
> 
>   as.POSIXct(as.POSIXlt(Sys.time(), tz = "CET"), tz =
"EST")
> 
> This only happens on Ubuntu Focal, it seems to work fine on Ubuntu
> Bionic. I am the standard ubuntu docker image icw/ r-base from Dirk's
> ppa:edd/r-4.0 on both systems.
works fine using the backported R 4.0.0 on Debian buster:

R> as.POSIXct(as.POSIXlt(Sys.time(), tz = "CET"), tz =
"EST")
[1] "2020-04-25 10:05:29 EST"

Johannes
> 
> Am I missing a system dependency for tzone data?
> 
> Jeroen
> 
> _______________________________________________
> R-SIG-Debian mailing list
> R-SIG-Debian at r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-debian

On Sat, Apr 25, 2020 at 10:41 AM Johannes Ranke <johannes.ranke at
jrwb.de> wrote:
>
> Am Samstag, 25. April 2020, 01:02:38 CEST schrieb Jeroen Ooms:
> > Hi all,
> >
> > I am testing R 4.0 and ran into an issue with timezones on Ubuntu
> > Focal: converting a timestamp to another timezone results in NA:
> >
> >   as.POSIXct(as.POSIXlt(Sys.time(), tz = "CET"), tz =
"EST")
> >
> > This only happens on Ubuntu Focal, it seems to work fine on Ubuntu
> > Bionic. I am the standard ubuntu docker image icw/ r-base from
Dirk's
> > ppa:edd/r-4.0 on both systems.
>
> works fine using the backported R 4.0.0 on Debian buster:
>
> R> as.POSIXct(as.POSIXlt(Sys.time(), tz = "CET"), tz =
"EST")
> [1] "2020-04-25 10:05:29 EST"
Perhaps the root cause of the change in behavior is that on the
focal/bullseye docker images, /usr/bin/timedatectl exists, but it does
not work:

   root at focal:/# timedatectl
   System has not been booted with systemd as init system (PID 1).
Can't operate.
   Failed to create bus connection: Host is down

R assumes that if it timedatectl exists, it can be used. On the docker
image of bionic and buster, timedatectl simply is not installed so R
does not call it.

The consequence though, is very subtle changes in behavior of time
conversion edge cases that I cannot explain. For example we get
differences between "UTC" and "Etc/UTC":
> Sys.timezone()
[1] "Etc/UTC"
# System has not been booted with systemd as init system (PID 1). Can't
operate.
# Failed to create bus connection: Host is down
Warning message:
In system("timedatectl", intern = TRUE) :
  running command 'timedatectl' had status 1

as.POSIXct(strptime("24.04.2020 01:00", format = "%d.%m.%Y
%H:%M", tz
= "CET"), tz = "")
[1] NA

as.POSIXct(strptime("24.04.2020 01:00", format = "%d.%m.%Y
%H:%M", tz
= "CEST"), tz = "")
[1] "2020-04-24 01:00:00 UTC"
> as.POSIXct(strptime("24.04.2020 01:00", format = "%d.%m.%Y
%H:%M", tz = "CET"), tz = "Etc/UTC")
[1] NA
> as.POSIXct(strptime("24.04.2020 01:00", format = "%d.%m.%Y
%H:%M", tz = "CET"), tz = "UTC")
[1] "2020-04-24 01:00:00 UTC"