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

[Jean Louis <bugs@gnu.support>]

* Max Nikulin <manikulin@gmail.com> [2023-02-05 20:06]:
> On 05/02/2023 01:59, ypuntot wrote:
> > Then, given the time zone and the local time, you can know UTC.
> > If orgmode gets the UTC there is not ambiguity.
> 
> Mapping from local time to UTC may be ambiguous, so mapping from local time
> to time zone offset may be ambiguous as well.

Okay, though explain practical case examples.

Local time to UTC is almost always used in computing for accurate log
purposes.

Using UTC time for future events is vague, for reason that other human
cannot know with certainty what the author intended to do. Maybe
author intended meeting at 10 o'clock, but UTC offset in author's or
participant's time zone changed, or even time zone entry is not any
more. Author maybe had UTC offset -5, but now is -7, it becomes vague
what time author really intended.

Local time to time with UTC offset for same reason could be
non-conclusive in future.

Past is alright, as local time with UTC offset is pretty certain as
time zones hardly change in past.

Org needs first use examples, and then implementation for use examples.

> Usual case is local time change due to daylight saving time. Notice that 2nd
> and 4th lines in the results table have the same input, but time offset
> differs by 1 hour in the output while local time is the same:

Which is good example to demonstrate to people that 2:30 o'clock alone
cannot be represented in such time zones without UTC offset. That
"02:30" appears twice, it does not mean it is ambigous, as UTC offset
or different name of time zone like CET, CEST, would indicat what time
is that exacctly.


-- 
Jean

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