Convert between timezones (was: How to re-write this bash script in Python?)

[Thomas 'PointedEars' Lahn]

[X-Post & F'up2 comp.unix.shell]

Chris Angelico wrote:

> On Fri, Jul 31, 2015 at 6:15 PM, Cameron Simpson <c...@zip.com.au> wrote:
>> Actually, bash has no timezone support but the date command _does_, and
>> probably neither better nor worse than Python. All one has to do is set
>> the TZ environment variable, eg (untested):
>>
>> _year_gmt=$( TZ=GMT date +%Y )
>
> That's assuming that it's converting against the current system
> timezone. I don't know how you'd use `date` to convert between two
> arbitrary timezones. […]

With POSIX date(1), ISTM all you could do is set the system time and for an
additional invocation the TZ variable accordingly for output.

<http://pubs.opengroup.org/onlinepubs/9699919799/utilities/date.html>

With GNU date(1):

$ (tz_source="Asia/Dubai"; time_source="$(LC_TIME=C TZ=$tz_source date -d
"today 00:00 UTC+4" -Im)"; tz_target="America/Chicago"; echo "When it was
$time_source in $tz_source, it was $(LC_TIME=C TZ=$tz_target date -d
"$time_source") in $tz_target.")
When it was 2015-07-31T00:00+0400 in Asia/Dubai, it was Thu Jul 30 15:00:00
CDT 2015 in America/Chicago.

$ date --version
date (GNU coreutils) 8.23
[…]

:)

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PointedEars

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