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>]

* Ihor Radchenko <yantar92@posteo.net> [2023-02-05 13:45]:
> [2024-02-04 12:00 @-08,America/Vancouver] will use fixed -8 offset

What does that mean practically? Provide example for better
understanding. 

- The UTC offset is not certain to remain fixed in the future. 

- If you do not have the time of creation of the timestamp above, you
  cannot know with certainty what was the offset in past, to calculate
  new UTC offset in case it changed

- As not even time zone is certain to remain in existence in future,
  you will need to use time zone, in order to derive that future UTC
  offset correctly. As it could change in mean time.

What is meaning of "fixed -8 offset"?

> [2024-02-04 12:00 @-08] will also use fixed -8 offset

That type of timestamp does not clearly show the time zone, that one
may only be understood as timestamp with UTC offset. UTC time may be
derived from such timestamp. That offset should remain fixed, as there
is no time zone associated. It is UTC time represented with offset.

> [2024-02-04 12:00 @America/Vancouver] will use @America/Vancouver time
> zone, as it is be defined in you OS time zone database.

If you do not keep UTC offset, you will miss changes in future and
generate errors.

> [2024-02-04 12:00 @-08,!America/Vancouver] (note "!") will use fixed -8
> offset, but also calculate America/Vancouver time from TZ database,
> compare it with the time coming from -8 offset, and warn you if there is
> inconsistency.

The UTC offset is the log what was the UTC offset at the time point
when timestamp was created, as future UTC offset cannot be known.

Making it "fixed" does not fix it in real time, you are then
introducing something new than what other programs do with time.

I do not think that you need "!", you are creating work not necessary
for users.

If users wish to get some warnings, let them customize single option.

Not timestamp by timestamp.

--
Jean

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