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Comment by masklinn | Hacker News Reader

It’s really not clear what you’re asking.

The point of using zoned events is to match the life and expectation of people living in the real world e.g. if there is a meeting in Perth at 10AM, and the Perth timezone gets shifted, the meeting is still occurring at 10AM perth time. If it’s broadcast then every other time is what changes (or not).

If people want to fix their meeting internationally they can already do that by setting their meeting time in UTC.

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> future zoned datetime carry outright uncertainty as to their actual location on the timeline (as the zone’s offset can be updated at any point and any number of times until the event has elapsed)

I wondered if it would be worth applying a (optional?) version to a timezone when stored, so you could distinguish between "whenever it is this time in Perth" vs "when I currently think this time will be in Perth, though if Perth changes its mind on how it offsets time, I want to keep what time I currently think that will be".

But you're right, that doesn't really add anything over storing it as UTC.

The fix is storing the datetime without a timezone, so the hour stays stable, no matter what the timezone of Perth does, plus optionally and separately the location (Perth), which could be stored as the timezone id of the location. But you could also use coordinates. Anything which can be mapped to its timezone later works. Now the time will never change for the original location (sic), and you can always compute the time for any timezone in the world, because in the instance of computation, you take the current valid timezone of the location, and you apply that to the stable datetime. Of course a current computation of that might have a different value in the future. But that doesn't matter, since the time for the original location (sic) never changes, and the value for different timezones is supposed to change.

> if there is a meeting in Perth at 10AM, and the Perth timezone gets shifted, the meeting is still occurring at 10AM perth time.

The thing about this is that if Perth's time zone ever changes so erratically or with such little notice that participants need to be notified that the point-in-time of an upcoming meeting has changed, it's no longer clear whether the participants would actually want the zoned "Perth at 10am" time to be canonical.

If athletes were flying in from around the world for an international competition tomorrow at 10am, and Australia decided to increase Perth's UTC offset by 1 hour as of today, would we expect all athletes, organizers, fans, etc. to show up and do everything 1 hour earlier (by solar time)?

> The thing about this is that if Perth's time zone ever changes so erratically or with such little notice that participants need to be notified that the point-in-time of an upcoming meeting has changed

"erratically" and "with little notice" are pretty relative when it comes to timezone shifts. DST decisions have been made with as little as a week lead time, Samoa dropping an entire day off of its calendar was done with under a year lead time (noises started about 9 months prior, the act was assented 6 months prior).

> would we expect all athletes, organizers, fans, etc. to show up and do everything 1 hour earlier (by solar time)?

Usually yes.

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