Comment by jolmg
5 months ago
> Let PDT be PDT(-8) and PST be PST(-7). Why do I need to choose Cupertino, CA (or LA in the blog post example)
Whether daylight savings time is being used at a given location at a given time of year is a matter of government policy. The city-based timezone selectors should handle that automatically based on the jurisdiction you choose.
> Sure, it's duplicate data but a backend system (Postgres config files, say) should only store the value of the TZ, i.e. -7 / -8.
Then the time may be wrong for half the year depending on where you are.
> The city-based timezone selectors
There's no America/Salt_Lake_City you're recommended to use America/Boise instead. The people in Salt Lake City are about as far away from Boise as you can get and Salt Lake City is more easily recognized as a landmark then Boise. The process of choosing which cities should be landmark cities comes across as faulty and uninformed.
The reason why certain cities get entries is because sometime after time began (1970-01-01), the region they're in changed their timezone (usually adopting or dropping DST or changing when it began). Those changes need to be recorded in the timezone database. The largest city in the affected area is typically chosen to be representative of the area.
Boise has its own entry because in 1974, the Emergency Daylight Time Act shifted when DST began in Southern Idaho and eastern Oregon. Boise is the largest city in the region.
Technically, if you're in Salt Lake City, you should be using America/Denver, not Boise because of this, otherwise if you say, opened a calendar from 1974, everything will be off by an hour.
If Utah made DST there begin a day earlier this year, Salt Lake City would probably get an entry too.
I think for the US, they should ensure tzdata contains at least one city for every state. That’s what they do for Australia. Now, it so happens their current rules-only add city if in recent decades it had distinct time zone rules-happen to produce that outcome for Australia, because in Australia time is a state issue and historically every state decided for itself whether to have daylight savings and when to begin/end it. Still, I think they should amend their rules to say “capital and/or largest city for every first-level subdivision of major countries”, given some reasonably objective definition of “major” (e.g. G20 nations)
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> Those changes need to be recorded in the timezone database.
The issue with this thinking is that all existing datimes referring to that region will continue using the old timezone because the new one didn't exist yet.
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Salt Lake City is a 4.5-5 hour drive from Boise. If you want a better example, there are no cities in Texas in the list, and Chicago is a lot further away than Boise is from Salt Lake City!
Yep, I pick Chicago for my timezone and it's roughly a 7 hour drive. I think have major cities represent broad timezones is a good UX tradeoff.
> The process of choosing which cities should be landmark cities comes across as faulty and uninformed.
I think it's unlikely they're chosen as landmark cities. More likely, timezones were uniform, then some government likely did their own thing in their jurisdiction. The change was then represented as a new timezone named after the place where the change is centered. IOW, the names have more to do with some random divergence that happened at some point in history, rather than what landmarks are the most recognized for today's timezones. Re: Boise & Salt Lake City, maybe Boise was the first to do their own thing while Salt Lake City had a different timezone. Maybe Salt Lake City later decided to adjust their timezone to fit Boise's to facilitate commerce between their states.
I run all my clocks and computers in UTC. I hate that I have to select "Reykjavik" in the Ubuntu installer instead of just "UTC".
Have you had any interesting pros/cons to running your clocks UTC?