RFC: Timestamps/timezones proposal

[Charles Day]

On Fri, Jul 18, 2008 at 11:29 AM, Derek Atkins <warlord at mit.edu> wrote:

> Graham Leggett <minfrin at sharp.fm> writes:
>
> > Charles Day wrote:
> >
> >> Tell me how this proposal would cause "random" date changes. Only
> >> the *display* of the timestamp changes, and only according to
> >> settings that you pick yourself.
> >
> > Try this:
> >
> > Enter a transaction dated 1 March 2008 in an account with timezone
> > UTC+02, with its split in a second account with a timezone of UTC.
>
> Okay, so the transaction would have an internal timestamp of
> "2008-03-01 12:00:00 UTC".  In UTC+02 this gets displayed as
> 2008-03-01.  It will also be displayed as 2008-03-01 in the
> UTC-TZ account.
>
> > Later, the user notices that in the second account, the transaction
> > appears on 29 Feb 2008, goes "that's odd", and "corrects" the date to
> > say 1 March 2008.
>
> Nope, it will be 2008-03-01 in both accounts.
>
> > Without the user knowing, the transaction on 1 March is now actually
> > on 2 March 2008.
>
> Nope.  See above.
>
> [snip]
>
> Having said all that, I'm beginning to believe that for the
> POST Date I think it should ALWAYS be in UTC and always be
> displayed as UTC, regardless of the local timezone.
>

That's what I'm suggesting would happen for those users who don't choose to
enable "time of day" or "multiple time zone" features (and these two
features are separate things!).

However, if a feature for entering "time of day" will not be supported, even
in a fixed time zone, then I see no point using timestamps; might as well
just use dates alone.


> Before you get yourself in a snit, let me explain what I
> mean.
>
> When *entering* a date, we take the entered string (e.g. 2008-07-18)
> and create a UTC timestamp of 12:00:00 on that date in UTC.
> So it doesn't matter that we're in UTC+14, we see that the
> local date is July 18 so we create a July 18 noon-UTC timestamp.
>
> When displaying a date, we take the UTC conversion of the
> UTC timestamp and display it.
>
> voila -- we now have "dates" using time_t.
>
> -derek
> --
>       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
>       Member, MIT Student Information Processing Board  (SIPB)
>       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
>       warlord at MIT.EDU                        PGP key available
>

-Charles