On Mon, 30 May 2011, Jakub Narebski wrote:
> > > Why not use UTC+N timezone [â]?
>
> I think full specification is UTC+HH:MM or UTC-HH:MM. GNU date
> understands 'TZ=UTC+09:30 date'.
No, thatâs not what the letter code in TZ means. TZ=EDT+04:00 means that
â The current time zone is called EDT.
â The current time zone is at offset -04:00 from UTC. (Note the sign
reversal.)
EDT is displayed as the name of the zone and is not used in any
calculations; it does not mean weâre taking an offset _from_ EDT.
So it doesnât make sense to write TZ=UTCÂNN:NN for any NN:NN other than
00:00. Otherwise libc will happily give you the nonsense that you asked
for:
$ TZ=UTC+00:00 date; TZ=UTC+09:30 date
Mon May 30 21:21:32 UTC 2011
Mon May 30 11:51:32 UTC 2011
This is why I used âUnknownâ instead of âUTCâ.
(Oh, my comment should have said âUnknownÂNN:NNâ instead of
âUnknownÂNNNNâ; the code gets it right.)
If I wanted to do better, Iâd need a way to translate UTC offsets to zone
names, but I donât know of a canonical way to do that (thereâs not even a
unique answer in general).
In Tcl â 8.5, none of this matters because âclock format -timezoneâ just
uses the numerical UTC offset as the zone name. For the fallback code, I
canât do that by manipulating TZ, because the zone name needs to be made
of letters.
Anders
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