Re: [FEATURE REQUEST] Timezone support in org-mode datestamps and org-agenda

[Ihor Radchenko <yantar92@posteo.net>]

Daryl Manning <daryl@wakatara.com> writes:

> I'd just be excited to have us run through the basic use cases and then see
> some more "tricky" ones. I imagine there are things we'd just have to
> say... too tricky for (eg. flight takes off in one TZ and range allows it
> to land in timezone... stuff like that might be tricky.).

https://www.youtube.com/watch?v=-5wpm-gesOY gives various examples.
To summarize:

1. Time (YYYY-MM-DD HH:MM) not continuous and may change arbitrarily at
   certain times a year or in future or in the past:
   - DST transitions are not stable and change from year to year
     according to strange rules that may involve Julian dates or
     counting weekdays
   - DST transition rules may change over time
   - The new year day itself is not necessarily fixed (England
   - Julian/Gregorian transitions happened at different times in
     different countries

2. There might be arbitrary time gaps due to time transition, including
   time overlaps with the same time of the day happening multiple time a
   day:
   - One hour back during DST transition (northern and southern
     hemispheres do the transitions in opposite directions)
   - Multiple days skipped (Samoa skips a whole day during DST
     transition)
   - Great Britain used 2 hours DST offset during WWII
   - Julian/Gregorian calendar transitions in the past

3. We cannot assume that the same geographical area has fixed time zone
   even at given point of time:
   - Palestinian/Israeli people follow different time zones in the
     contested territories

4. Great Britain had new year on March 25 until 16th century
   (March 24, 1000 -> (+1 day) March 25, 1001)

5. Leap seconds! 23:59:59 -> 23:59:60 -> 00:00:00, according to
   astronomical Earth observations

> So, is the TS syntax you've described accepted and canonical now with
> org-mode?

We are still discussing it.

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