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

[Jean Louis]

* Ihor Radchenko <yantar92@posteo.net> [2023-01-31 16:46]:
> Specifying just @Europe/Berlin is ambiguous around the daylight savings
> transition.

Sorry, I cannot see practical example why is it ambiguous. Unless
programmer does not take all information in account, it is not
ambigous. People on this planet agree on time zones in advance, so
there are few changes that people cannot plan in advance.

Those changes are recorded in time zone databases.

Unless you consider programming without using time zone databases,
then I can surely understand that it will be ambiguous. 

> To resolve the ambiguous, we should either introduce DST flag

DST is property of time zone. You do not introduce it, you read it
from time zone database.

But maybe you wish to implement time zones in Org.

In that case I can only say "Good luck" to accuracy.

> or simply allow specifying the UTC offset directly.

UTC offset is not reliable, and is also derived from time zone
database. 

Try it out, make tests, create experiments, compare if that approach
will be usable, publish it and put in for testing.

> Since DST is not guaranteed to be +-1 hour (it may be more, up to 1
> full day), DST flag is more problematic than UTC offset.

Is not if you always pull the latest tz database. Political changes
are pretty careful to people and decisions are announced ahead of the
change.

So do you think that you cannot use tz database in Emacs Lisp?

Maybe it will be necessary to make new Lisp functions defined in C
language, accessing the time zone database.

But it is not for Org to implement new tz database in Emacs Lisp, that
will become unmaintainable work. But why not, if you wish, but
accuracy of time will be questionable.

Researching following pages will give you idea with what you are
trying to deal with on Org level:

How to Read the tz Database:
https://data.iana.org/time-zones/tz-how-to.html

List of tz database time zones - Wikipedia:
https://en.wikipedia.org/wiki/List_of_tz_database_time_zones

tz database - Wikipedia:
https://en.wikipedia.org/wiki/Tz_database

-- 
Jean

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