* Tim Cross <theophil...@gmail.com> [2023-02-01 11:10]: > I think the confusion relates to context interpretation. If you see > @Europe/Berlin in isolation, then it is ambiguous as it can refer to > two different time zone definitions (standard v daylight savings).
Of course, without the time stamp, the time zone alone cannot give time. > However, if you consider it in conjunction with a date and time, as > in 2023-03-23 02:30 @Europe/Berlin, then it isn't ambiguous - in > that case, it really just says 'Lookup the time zone offset in the > databse for Berlin as of that date and time. Exactly that. > Now that could change - for example, the German government might > make a temporary or permanent change that would change the offset > from UTC for that date+time the day after I look at it (or export > it). It cannot change in past. It will not change drastically or capriciously as Germany aligns with other countries and ISO standard. It is more likely that ISO non-members deviate from international coordination of time related definitions: ISO - Members: https://www.iso.org/members.html > Personally, I cannot see the use case of including both a fully > qualitifed time zone (as in @Europe/Berlin) and an offset, but I > also don't know all possible use cases - there could well be use > cases where you want/need to record both the location time zone as > well as the offset at the point when you recorded the timestamp. Time Zones vs. Offsets – What's the Difference? Which Is Best?: https://spin.atomicobject.com/2016/07/06/time-zones-offsets/ Quoting: -------- - Given a time zone and a UTC time, you can know the offset—and therefore the local time. - Given a local time and an offset, you can know UTC time, but you do not know which time zone you’re in (because multiple timezones have the same offset). - Given UTC and an offset, you can know the local time. - Given a time zone and an offset, you don’t know much. - That’s why a calendar systems work with time zones, offsets, and UTC; - we need the offset to go from local time to UTC, and we need the time zone to go from UTC to local time. -- Jean Take action in Free Software Foundation campaigns: https://www.fsf.org/campaigns In support of Richard M. Stallman https://stallmansupport.org/