Jean Louis <bugs@gnu.support> writes: > * Ihor Radchenko <yanta...@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>
