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by masklinn 1179 days ago
> Lot of confusion here. UTC is a time standard, not a particular time zone. An instant written down in, say, the Pacific Standard Time Zone can be a UTC-scaled time.

UTC is very much a timezone, that’s why it has a timezone designator (Z).

If you record a future PST date as UTC and PST changes, your recorded date is now wrong.

> So for a date to be “in UTC” really just means it uses the leap seconds published by IERS. This article says “integers in UTC” which is a little ambiguous, but probably means “integer UTC seconds since the Unix Epoch.”

And that’s guaranteed to fuck up for future local events.
2 comments
vardump 1179 days ago
> If you record a future PST date as UTC and PST changes, your recorded date is now wrong.

Damn. That's a very good point. From now on, I'll be always recording also timezone, especially when it comes to future dates!

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baq 1179 days ago
Any timezone you want, as long as it's UTC. (If above scares you, think about how to record an event that should happen 5th of November 2023 1:30 AM PST.)
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spenczar5 1179 days ago
> UTC is very much a timezone, that’s why it has a timezone designator (Z).

This is just not correct. The "Z" is a historical maritime designation for the zero-point timezone, GMT, and predates UTC by decades.

UTC is defined by the International Telecommunications Union in recommendation TF.460-6 (pdf link: https://www.itu.int/dms_pubrec/itu-r/rec/tf/R-REC-TF.460-6-2...). It's brief and you won't find any mention of time zones.

The symbolism "UTC+0" or the "Z" timezone come from ISO-8601, which is a specification for how to represent times in strings. You can find that specification here: https://web.archive.org/web/20171019211402/https://www.loc.g...

See section 2.1.12 Note 3:

> UTC is not a time zone, it is a standard. UTC is also not GMT (Greenwich Mean Time), rather, UTC has replaced GMT. UTC is more precise; the term 'GMT' is ambiguous.

That document goes to great lengths to keep this distinction between time scales and time formats. They're different, and conflating them will get you very confused. When you describe a time in PST, you are almost certainly using UTC.

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