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The top level comment said > specify a meeting in London, on July 1st 2030, at 6pm local time - no matter what happens to UK timezones between now and then GP

The top level comment said > specify a meeting in London, on July 1st 2030, at 6pm local time - no matter what happens to UK timezones between now and then GPS coordinates + local date and local time will preserve “a meeting in London, on July 1st 2030, at 6pm local time” in the desired way

jvanderbot 3y ago
How: 6PM local time could mean Zulu+6 or Zulu+3 or anything else if local timezone offset changes via legislation. The best way to do it would be to say "X seconds from the time this message was sent"
- avianlyric 3y ago
  > 6PM local time could mean Zulu+6 or Zulu+3 or anything else if local timezone offset changes via legislation. That’s the point. Normal people think about time based on their local time. If they agree to meet someone at 3pm on a day in the future, that normally means turning up on that day when a local clock on that day reads 3pm. If local time changes offset from UTC, then the meeting implicitly also changes. I’ve personally yet to meet someone that reschedules all their appointments every time day light saving (or the inverse) rolls around. Just make sure their appointment times in UTC don’t change.
- noselasd 3y ago
  "X seconds from the time this message was sent" would certainly not hit 6PM local time if the local timezone offset changed - unless you also update X every time it does.
- kelnos 3y ago
  +6 or +3 is irrelevant to the scheduler when they're setting the meeting time: they want it to be 6pm regardless of any time zone changes in the future. So they deliberately do not store the UTC offset with that time. They only store the geographic location. Then when the meeting time is approaching, the software can figure out what time zone (and UTC offset) applies, after taking account any time zone changes that have taken place in the intervening years, and appropriately set reminder notifications. If they were to store "X seconds from the time this message was sent", then any time zone change would likely make it not fall at 6pm on the target day, so that's not what they'd want.

jvanderbot 3y ago

How: 6PM local time could mean Zulu+6 or Zulu+3 or anything else if local timezone offset changes via legislation. The best way to do it would be to say "X seconds from the time this message was sent"

avianlyric 3y ago
> 6PM local time could mean Zulu+6 or Zulu+3 or anything else if local timezone offset changes via legislation. That’s the point. Normal people think about time based on their local time. If they agree to meet someone at 3pm on a day in the future, that normally means turning up on that day when a local clock on that day reads 3pm. If local time changes offset from UTC, then the meeting implicitly also changes. I’ve personally yet to meet someone that reschedules all their appointments every time day light saving (or the inverse) rolls around. Just make sure their appointment times in UTC don’t change.
noselasd 3y ago
"X seconds from the time this message was sent" would certainly not hit 6PM local time if the local timezone offset changed - unless you also update X every time it does.
kelnos 3y ago
+6 or +3 is irrelevant to the scheduler when they're setting the meeting time: they want it to be 6pm regardless of any time zone changes in the future. So they deliberately do not store the UTC offset with that time. They only store the geographic location. Then when the meeting time is approaching, the software can figure out what time zone (and UTC offset) applies, after taking account any time zone changes that have taken place in the intervening years, and appropriately set reminder notifications. If they were to store "X seconds from the time this message was sent", then any time zone change would likely make it not fall at 6pm on the target day, so that's not what they'd want.