[DB-SIG] DateTime: Changing the time value handling ?!
Wed, 11 Mar 1998 08:51:08 -0500
Greg Stein (Exchange) wrote:
> Why should Unix ticks be any different from the others? All of the times are
> absolute with respect to an unknown time zone. You have NOT picked any time
> zone. If you generate a ticks value, then somebody should use that with
> respect to the proper time zone.
> Generally, the only point where a time zone becomes apparent is when people
> use something like the .Format() method (or time.ctime()) and the output
> includes a time zone string.
It also comes in to play when you do math on times. 9pm EST - 8pm PST
is *not* one hour.
These sorts of issues are important if you have to deal with times
from multiple time zones, or use time data from one time zone in
> It sounds like people are mixing time zones values. e.g. they create a
> DateTime assuming it is within the current time zone, but then pass it to a
> function in the time module that expects a UTC time (or vice versa).
> A large part of the discussion has historically fallen around time zone
> handling. The unofficial consensus has always come out of that with "don't
> build time zone information into the base types" (let higher levels deal
> with it)
The ODMG standard includes time zone in it's Time and Timestamp classes.
They take a fairly minimalist approach. Their time zones are just
from UTC. They leave deciding *what* the offset is (e.g. dealing with
daylight savings time) to the application.
> I would highly recommend the absolute avoidance of anything that infers /
> implies time zones within the base data types.
I disagree with this statement, although not entirely. As I have
said before, I think the Date-Time classes should be based on the
ODMG standard which provides a *mimimalish*, but useful, treatment
of time zones.
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