Re: [POLL] Proposed syntax for timestamps with time zone info (was: [FEATURE REQUEST] Timezone support in org-mode datestamps and org-agenda)

[Ihor Radchenko]

Jean Louis <bugs@gnu.support> writes:

>>    For time ranges, we will only allow a single offset and time zone
>>    specifier for both start and end times:
>>    [2022-11-12 8:00-9:00+08]
>>    If different time zones are necessary to specify the start/end times,
>>    users can still use full timestamp range syntax
>>    [2022-11-12 8:00+03]--[2022-11-12 22:00+08]
>
> I have already explained today that above calculation cannot be
> unambigous. Please verify my references and practical examples. When
> user thinks that span is X hours, the real span could be X-1 or X+1

This has been discussed in the previous emails.
Consider that you are running a scientific experiment around daylight
saving time change: [2022-10-29 2:15-5:15+02]. You don't care that the
government decided that the wall clock should go like 2:15 -> 2:59 ->
[CEST -> CET] 2:00 -> 2:15 -> 2:59. Physics does not care. You just need
to make sure that the experiment runs exactly 3 hours without trying to
consider the currently used TZ rules. In contrast, writing [2022-10-29
2:15-5:15 @Europe/Berlin] is ambiguous as it may imply both
2:15CEST-5:15CET (4 hours) or 2:15CET-5:15CET (3 hours).

Specifying just @Europe/Berlin is ambiguous around the daylight savings
transition. To resolve the ambiguous, we should either introduce DST
flag or simply allow specifying the UTC offset directly. Since DST is
not guaranteed to be +-1 hour (it may be more, up to 1 full day), DST
flag is more problematic than UTC offset.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
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