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From: | Daryl Manning |
Subject: | Re: [FEATURE REQUEST] Timezone support in org-mode datestamps and org-agenda |
Date: | Tue, 17 Jan 2023 10:55:01 +0700 |
Ihor Radchenko <yantar92@posteo.net> writes:
> Robert Horn <rjhorn@panix.com> writes:
>
>>> 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
>>
>> Note that as a result "time when it happened" has different rules than
>> "future time when it is scheduled". There are lots of other times that are
>> scheduled as "future local time, subject to changing DST rules". This
>> is particularly tricky for repeating times for regularly scheduled events.
>
> Not really. Countries may change DST at any moment in future. Or decide
> to switch calendars (consider countries near the day transition line).
>
> And "past local time, according to the DST rules in effect at the time"
> is also an option that might be useful in certain scenarios.
>
The issue is clarity of the expected rules for the format. If I
schedule a meeting for 10:05 DST, but the rules change so that it is not
DST at that location at that time in the future, what is the expected
interpretation? It could be:
a) the meeting should be at 10:05 ST, because the intent was to meet at
10AM in the then local time.
b) the meeting should be at 11:05 ST, because the time was chosen to
correspond to a particular sun angle.
Getting the rules and explanation clear is the issue. It's a mistake
that a great many people make with scheduling meetings. Those two
behaviors need different encodings because they behave differently.
--
Robert Horn
rjhorn@alum.mit.edu
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