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From: Ihor Radchenko <yantar92@posteo.net>
To: Jean Louis <bugs@gnu.support>
Cc: Ypo <ypuntot@gmail.com>, Org-mode <emacs-orgmode@gnu.org>
Subject: Re: [POLL] Proposed syntax for timestamps with time zone info (was: [FEATURE REQUEST] Timezone support in org-mode datestamps and org-agenda)
Date: Mon, 06 Feb 2023 14:10:58 +0000	[thread overview]
Message-ID: <87357i9959.fsf@localhost> (raw)
In-Reply-To: <Y9+dEGvIdSEFjdkg@protected.localdomain>

Jean Louis <bugs@gnu.support> writes:

> * 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. 

It means "when I scheduled this item, I expected the UTC offset at the
time of the timestamp to be -08 and remain so. It was motivated by
America/Vancouver time zone, but if it changes in future, I do not care
- the scheduled time should remain at specific time point relative to
UTC".

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

Yes. But fixing UTC offset means that time point is fixed. Example: you
need a timestamp exactly N hours from now. It must not be affected by
time zone rule changes.

> - 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

America/Vancouver in the above timestamp is nothing but a reference
comment. One may or may not use it.

> - 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.

If timestamp must follow the future time zone rules, can just use 
 [2024-02-04 12:00 @America/Vancouver]

>> [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.

Only if you care. Maybe it is not an error to follow the future changes.
If you want to be notified, just use [2024-02-04 12:00
@-08,!America/Vancouver] explicitly stating the offset you expect in
future.

>> [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.

Sure. -08 is expected offset.

> 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 understand this statement.

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

I hope that I clarified the need in the above examples. You may also
refer to the reference in the original proposal. The idea with "!" is
explained in more details.

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

This will be less fine-grained approach. For some timestamps, you don't
need warnings. Of course, default customization may be also provided to
enable warnings for timestamps without "!".

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>


  parent reply	other threads:[~2023-02-06 14:11 UTC|newest]

Thread overview: 90+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-04 21:38 [POLL] Proposed syntax for timestamps with time zone info (was: [FEATURE REQUEST] Timezone support in org-mode datestamps and org-agenda) Ypo
2023-02-05  3:12 ` Max Nikulin
2023-02-05  9:31 ` Jean Louis
2023-02-05 10:44 ` Ihor Radchenko
2023-02-05 12:12   ` Jean Louis
2023-02-05 13:01     ` ypuntot
2023-02-06 14:15       ` Ihor Radchenko
2023-02-07 21:38       ` Jean Louis
2023-02-06 14:10     ` Ihor Radchenko [this message]
2023-02-07 22:19       ` Jean Louis
2023-02-08 10:36         ` Ihor Radchenko
2023-02-10  3:29           ` Jean Louis
2023-02-10 10:48             ` Ihor Radchenko
2023-02-12  9:33               ` Jean Louis
2023-02-12 13:47                 ` tomas
2023-02-14  6:00                   ` Jean Louis
2023-02-14  9:41                     ` Heinz Tuechler
2023-02-14  9:45                       ` tomas
2023-02-14 11:42                         ` Max Nikulin
2023-02-14 15:59                           ` Jean Louis
2023-02-14 16:45                             ` Thomas S. Dye
2023-02-16 14:21                               ` Jean Louis
2023-02-14 16:57                             ` Max Nikulin
2023-02-14 10:45                       ` Jean Louis
2023-03-10 10:46                         ` Ihor Radchenko
2023-03-08 13:30                 ` Ihor Radchenko
2023-03-10  1:37                   ` Jean Louis
2023-02-11  4:44             ` Max Nikulin
2023-02-12 10:32               ` Jean Louis
2023-02-15 15:17                 ` Ihor Radchenko
2023-02-16 15:06                   ` Jean Louis
2023-03-10 10:51                     ` Ihor Radchenko
2023-03-15 14:42             ` Max Nikulin
  -- strict thread matches above, loose matches on Subject: below --
2023-02-12 13:27 Ypo
2023-02-04 18:59 ypuntot
2023-02-04 19:45 ` Jean Louis
2023-02-05 17:04 ` Max Nikulin
2023-02-07 21:46   ` Jean Louis
2023-01-17  3:55 [FEATURE REQUEST] Timezone support in org-mode datestamps and org-agenda Daryl Manning
2023-01-17  8:22 ` Tim Cross
2023-01-17  9:15   ` Ihor Radchenko
2023-01-17  9:45     ` Tim Cross
2023-01-18  9:15       ` Ihor Radchenko
2023-01-18 11:43         ` Tim Cross
2023-01-18 12:02           ` Ihor Radchenko
2023-01-18 21:16             ` Tim Cross
2023-01-19  5:29               ` Jean Louis
2023-01-19  7:23                 ` Tim Cross
2023-01-19 14:32                   ` Jean Louis
2023-01-19 20:09                     ` Tim Cross
2023-01-19 23:02                       ` Thomas S. Dye
2023-01-19 23:51                         ` Tim Cross
2023-01-20  0:24                           ` Thomas S. Dye
2023-01-20  3:46                             ` Tim Cross
2023-01-20  6:14                               ` Thomas S. Dye
2023-01-27  6:06                                 ` Sterling Hooten
2023-01-27 11:09                                   ` Ihor Radchenko
2023-01-30 11:25                                     ` Greg Minshall
2023-01-31 11:48                                       ` [POLL] Proposed syntax for timestamps with time zone info (was: [FEATURE REQUEST] Timezone support in org-mode datestamps and org-agenda) Ihor Radchenko
2023-01-31 12:19                                         ` Daryl Manning
2023-01-31 12:41                                           ` Ihor Radchenko
     [not found]                                             ` <CAL9aZksf8AGF=dXg0KAtLPyu1ATt1fLpvdsjN6GMCuK2KRQ56w@mail.gmail.com>
2023-01-31 13:33                                               ` Ihor Radchenko
2023-01-31 13:22                                         ` Jean Louis
2023-01-31 13:46                                           ` Ihor Radchenko
2023-01-31 19:59                                             ` Jean Louis
2023-02-01 12:42                                               ` Ihor Radchenko
2023-02-01 15:28                                                 ` Jean Louis
2023-02-01 16:30                                                   ` Ihor Radchenko
2023-01-31 20:12                                             ` Jean Louis
2023-02-01  5:46                                               ` tomas
2023-02-01  7:29                                                 ` Jean Louis
2023-02-01  7:52                                                 ` Tim Cross
2023-02-01  8:32                                                   ` Jean Louis
2023-02-01  8:46                                                   ` Ihor Radchenko
2023-02-01  9:38                                                     ` Tim Cross
2023-02-01 10:15                                                       ` Ihor Radchenko
2023-02-01 14:53                                                         ` Jean Louis
2023-02-01 16:36                                                           ` Ihor Radchenko
2023-02-01 10:46                                                       ` Max Nikulin
2023-02-01 14:43                                                       ` Jean Louis
2023-02-01 16:45                                                         ` Ihor Radchenko
2023-02-02  3:05                                                           ` Max Nikulin
2023-02-02  8:59                                                             ` Ihor Radchenko
2023-02-01 14:38                                                     ` Jean Louis
2023-02-01 16:50                                                       ` Ihor Radchenko
2023-02-01  7:00                                               ` Thomas S. Dye
2023-02-01  7:41                                                 ` Jean Louis
2023-01-31 18:56                                         ` Greg Minshall
2023-02-01 12:48                                           ` Ihor Radchenko
2023-02-01 12:52                                             ` tomas
2023-02-02  4:49                                               ` Greg Minshall
2023-01-31 20:41                                         ` Tim Cross
2023-01-31 23:50                                         ` Samuel Wales
2023-02-01 13:01                                           ` Ihor Radchenko
2023-02-04 22:33                                             ` Samuel Wales
2023-02-04 22:49                                               ` Samuel Wales
2023-02-05 10:38                                               ` Ihor Radchenko
2023-02-01 11:56                                         ` Christian Moe
2023-02-01 12:20                                           ` Ihor Radchenko
2023-02-01 15:41                                             ` Jean Louis
2023-02-02  8:38                                               ` Ihor Radchenko
2023-02-03 11:31                                                 ` Jean Louis
2023-02-04 10:58                                                   ` Ihor Radchenko
2023-02-04 19:32                                                     ` Jean Louis
2023-02-05  9:14                                                       ` Ihor Radchenko
2023-02-02  3:46                                         ` Timothy
2023-02-02  9:12                                           ` Ihor Radchenko
2023-02-02  9:12                                             ` Timothy
2023-02-02  9:20                                               ` Ihor Radchenko
2023-02-02  9:27                                                 ` Timothy

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