| > I think [ISO8601 date and time with offset info is] sufficient for all use cases everywhere. TLDR: Also, which timezone is used (not quite the same as offset) really does matter--UTC is great but you can't use it everywhere. ________ One of my favorite simple examples of this "here be dragons" for the new developer: Any system that schedules a future calendar-event. Such events are typically pegged, implicitly if not explicitly, to a particular timezone or geographic context. For example: "The company's Virtual Summit will occur on November 2nd at 1PM Elbonian Xtremesunshine Time, hosted out of our central Elbonian headquarters." In that scenario, it is impossible to know for sure how many seconds-from-now it will happen until the moment actually happens! "2023-11-02 13:00:00 EXT" is actually a contract or spec for recognizing a future condition, one that will shift if/when the relevant nation/province/city simply declares their clocks shall be set differently. So if the Elbonian government alters their daylight-savings switchover to occur earlier on 11-01 instead of 11-06, then the summit just moved. Even if you scheduled everything UTC all along... Well, now the summit is overlapping lunchtime for everyone in Elbonia, so it moved from their perspective. |
As you note, for some uses this _does_ make a difference and tracking which one you have can in these cases be important.