Comment by tshaddox
7 hours ago
The trouble is that you can't really make safe assumptions about whether to use the "sticky" paradigm or the "point-in-time" paradigm.
Sticky really only makes sense in two scenarios:
1. when all participants are assumed to be in the same geographic/political time zone for the foreseeable future (in which case the only advantage over point-in-time timestamps is future political changes to that region's time zone, like DST changes), or
2. when there's some privileged participant such that everyone else can assume events follow that participant's time zone (e.g. a company headquarters that moves very rarely, or an individual's personal wakeup alarms which can probably be assumed to follow their current location's time zone as they travel).
If you have a group of friends who like to stay in touch with regular group calls, and all/most of them are digital nomads who change their time zone of residence multiple times per year, you probably don't want the sticky paradigm.
In practice, if you have participants from different timezones, you agree on one "reference" timezone, which can be also UTC, as in your nomads example. You can consider UTC as just another calendar you can stick to (but you should just not hardcode this in software for this appointment use-case). You actually need a reference to be able to plan an event in the first place. Otherwise you don't know which time you can propose. You would need to propose a "fixed" time for every timezone which participates, but that doesn't work, because these times might not refer to the same physical instant, so the meeting would not be (fully) synchronized. So instead, you take some time from some timezone and translate that to all the other timezones. You can even see that in online games, where some of them have an official "server time", which is globally the same, helping players to meet at the same time instant. UTC itself is another examples of this, used e.g. for global navigation or air traffic control.
That "only advantage" is doing a lot to dismiss the actual use case of, say, everyone keeping appointments on their calendar when the legislature passes laws around time zone changes.