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

[Ihor Radchenko]

Jean Louis <bugs@gnu.support> writes:

>> >> [2022-11-12 14:00 @UTC+2]
>> >> [2022-11-12 14:00 @UTC-2:30]
>> >> 
>> >> are also fine within the proposed format.
>> >
>> > The above format is unclear to me. I look at timestamps every day, too
>> > many, often change them.
>> >
>> > I cannot understand what you mean.
>> 
>> See "std offset" format for TZ environment variable.
>> https://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html
>
> I understand that information on hyperlink.
>
> I do not understand how it is related to "UTC", a with "UTC" people do
> not put UTC offset.

Well. "UTC" there is rather arbitrary, but _some_ abbreviation is
required as per TZ spec. Could also be [2022-11-12 14:00 @BLAHBLAH+2]

I used "UTC+2" because it is how offsets are often represented.
For example, https://time.is/London is displaying the following:

    Time in London, United Kingdom now
    ...
    Time zone
    - Currently Greenwich Mean Time (GMT), UTC +0
    - Daylight saving time (British Summer Time (BST), UTC +1) starts March 26, 
2023

Note UTC +0 and UTC +1.
I've seen such format in multiple time websites.

On the other hand, TZ POSIX is reverse from what is commonly meant when
displaying UTC +1.

> It is either UTC as time zone and offset can be considered only ZERO,
> like +0, or it is NOT UTC as time zone, and there is offset to
> understand what was really the UTC. This latter is also explained in
> that hyperlink.

> So what do you really mean with such time stamp?
>

You are right. From the point of view of TZ POSIX spec, UTC+2 is not UTC
time zone and not a known time zone. Rather manual nautical time zone
with arbitrary name and fixed UTC offset (+2).

> I think it is incorrect time stamp. If you specify UTC, you do not
> specify UTC offset. 

It is a correct TZ value 🤷

-- 
Ihor Radchenko // yantar92,
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