Re: Parsing Date Strings with Time Zones in c++

James Kanze <>
Sat, 9 Oct 2010 12:01:09 -0700 (PDT)
On Oct 9, 5:05 pm, =D6=F6 Tiib <> wrote:

On 9 okt, 10:32, Jorgen Grahn <> wrote:


(If you *do* know the jurisdiction you should be OK. Timezone info (on
my machine) *does* have knowledge of plenty of jurisdictions;
/usr/share/zoneinfo is full of (among other things) DST rules for
places like restricted parts of Tasmania, a hut on the Bailey
Peninsula of Antarctica and so on.)

No. You are not OK. Jurisdictions do change as do their rules about
DST. Even if you know jurisdiction and present rules about DST for
that jurisdiction you may still fail if you lack information what were
DST rules there at 1985 when parsing such a date.

He'll be OK for any date in the present, and the not too distant
future. And as the rules change, his system will automatically
update its database with the new rules (not deleting the old
ones, which will still be used for past dates).

Overall all these abbreviations are pointless. "-06" is lot better
than "CST" or "Central Standard Time", "-05" is lot better than "CDT"
or "Central Daylight Time" and saying briefly that it was in Chicago
is outright asking for trouble. Even if jurisdiction of that village
hasn't changed recently it might in next ten years (but recorded time
may still stay important).

Overall, UTC is really the only thing that works. Otherwise,
yes: [+-]0430 is better than an abbreviation. But even if all
software miraculously changed today, you'd still be stuck with
timestamps generated in the past. Pretending we can ignore
things like CET is just wishful thinking.

James Kanze

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