Read the previous blog post [0] -- this one is disjointed without it. I dislike TZ selectors that use locations (cities, countries, etc.). 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) -- locations over 1k miles away from me? And while I certainly understand where Cupertino is and how it relates to my TZ, what if someone else doesn't? Cupertino isn't a major population center.
Anyway, poor UX. But of course TZ names could also be argued as poor UX. What if you just did PST/PDT as Los Angeles, CA; Oregon, OR, and Seattle, WA all on separate line items? 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. At least a user could recognize 'oh, I drive to xyz major city occasionally, that's the choice I want'.
To keep ranting, I checked macOS 15 TZ selector for PDT/PST. The selector itself is labeled "Closest city". It has numerous locations in California, a few in Nevada, and a couple in Mexico. No cities in Oregon, Washington, or Idaho (and Hyder, AK... neat [1]).
Closest is a stretch, like I said, over 1K miles from LA. But why several California cities, including minor ones like Oceanside (~175K people), but nothing in Oregon (Eugene, also 175K), Portland (652K), or Washington - Tacoma (220K), Seattle (740K). Note I did not look for the smallest city in the macOS CA list.
It's weird to me. Maybe it's because Oregon == Intel and Washington == Microsoft. ;-)
> 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.
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.
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!
You can't just go by time zone names because there are weird exceptions, like most of Arizona not doing DST. Then there's Indiana, which didn't do DST until 20 years ago, and there are some counties that switched time zones when the DST law took effect... if you're in one of those counties will you just accept old timestamps being an hour off? Granted, this gradually becomes less of an issue the further we get from the change. But nothing guarantees that there won't be further changes in the future.
And that's just the US, there's almost 200 other countries each with their own laws.
A bit of an edge case, but there's also the problem that the time zone you pick today might not be the time zone you have tomorrow: The jurisdiction you're in can change what their clocks use on an institutional whim.
It's very unlikely, but tomorrow some state or major city in PST could decide to add 15 minutes to all their wall clocks. Should your computer's clock change? That depends on what you're using it for...
Even abbreviations have issues. PST (UTC+8) is also Philippine Standard Time. EST could mean Eastern Standard Time in Australia, granted that nowadays is AEST.
Timezones are such a headache. Obviously even UTC for a location varies depending on the time of year.
Even the International Space Station shifted timezones from Houston time to UTC+0.
Curiosity and Perseverance's clocks are UTC but operations run on LMST (local mean solar time) Gale Crater and LMST Jezero Crater- their landing locations. That point is moot until humans start spinning up VMs on Mars which they will one day.
The problem is both the US and Australia have “EST/EDT” - the Australian version sometimes has an A stuck on the front to disambiguate it from the US timezone, but that isn’t always done (especially given some systems insist timezone abbreviations can be max 3 characters). And the problem with disambiguating on the basis of UTC offsets is you’d be surprised by how many people have no clue what any of them are. But “Americas” vs “Australia”, they’ll get that right
I suspect a large number of users might choose PST if in California, when they really mean PST/PDT. Or perhaps in the summer they would semi-correctly choose PDT.
Choosing a large city you know shares your time zone does make things a bit more “human“.
When you plan a future event for 5PM on September 2nd 2029 in Latveria, we can guess when that will occur, but don't really know because Dr. Doom could arbitrarily re-zone the country at any time. Or maybe the country won't even exist.
Future events are triggering conditions. Making a prediction and storing your prediction in UTC is a very bad idea, because your prediction might become wrong, and now you have no way to recalculate.
UTC helps store specific moments in time. Notably it does not solve for "dates" nor recurrence. Many of my hairs have been lost to third parties thinking they've created viable systems simply because they use UTC.
Discussion about previous article in series:
Debian 13, Postgres, and the US time zones - https://news.ycombinator.com/item?id=45218111 - Sept 2025 (142 comments)
Title should involve "US/*", not just "US".
Context on "THE ONE", a phrase used in this post, because it wasn't obvious to me initially.
https://rachelbythebay.com/w/2018/04/28/meta/
> I got to wondering... why did I pick "US/Pacific", anyway?
That's what the authority that defines the zone calls it. Using any other name is adding a useless layer of abstraction.
Read the previous blog post [0] -- this one is disjointed without it. I dislike TZ selectors that use locations (cities, countries, etc.). 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) -- locations over 1k miles away from me? And while I certainly understand where Cupertino is and how it relates to my TZ, what if someone else doesn't? Cupertino isn't a major population center.
Anyway, poor UX. But of course TZ names could also be argued as poor UX. What if you just did PST/PDT as Los Angeles, CA; Oregon, OR, and Seattle, WA all on separate line items? 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. At least a user could recognize 'oh, I drive to xyz major city occasionally, that's the choice I want'.
To keep ranting, I checked macOS 15 TZ selector for PDT/PST. The selector itself is labeled "Closest city". It has numerous locations in California, a few in Nevada, and a couple in Mexico. No cities in Oregon, Washington, or Idaho (and Hyder, AK... neat [1]).
Closest is a stretch, like I said, over 1K miles from LA. But why several California cities, including minor ones like Oceanside (~175K people), but nothing in Oregon (Eugene, also 175K), Portland (652K), or Washington - Tacoma (220K), Seattle (740K). Note I did not look for the smallest city in the macOS CA list.
It's weird to me. Maybe it's because Oregon == Intel and Washington == Microsoft. ;-)
[0] https://rachelbythebay.com/w/2025/09/11/debtz/
[1] https://en.wikipedia.org/wiki/Pacific_Time_Zone#United_State...
> 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.
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!
You can't just go by time zone names because there are weird exceptions, like most of Arizona not doing DST. Then there's Indiana, which didn't do DST until 20 years ago, and there are some counties that switched time zones when the DST law took effect... if you're in one of those counties will you just accept old timestamps being an hour off? Granted, this gradually becomes less of an issue the further we get from the change. But nothing guarantees that there won't be further changes in the future.
And that's just the US, there's almost 200 other countries each with their own laws.
A bit of an edge case, but there's also the problem that the time zone you pick today might not be the time zone you have tomorrow: The jurisdiction you're in can change what their clocks use on an institutional whim.
It's very unlikely, but tomorrow some state or major city in PST could decide to add 15 minutes to all their wall clocks. Should your computer's clock change? That depends on what you're using it for...
Even abbreviations have issues. PST (UTC+8) is also Philippine Standard Time. EST could mean Eastern Standard Time in Australia, granted that nowadays is AEST.
Timezones are such a headache. Obviously even UTC for a location varies depending on the time of year.
Even the International Space Station shifted timezones from Houston time to UTC+0.
Curiosity and Perseverance's clocks are UTC but operations run on LMST (local mean solar time) Gale Crater and LMST Jezero Crater- their landing locations. That point is moot until humans start spinning up VMs on Mars which they will one day.
> Let PDT be PDT(-8) and PST be PST(-7)
The problem is both the US and Australia have “EST/EDT” - the Australian version sometimes has an A stuck on the front to disambiguate it from the US timezone, but that isn’t always done (especially given some systems insist timezone abbreviations can be max 3 characters). And the problem with disambiguating on the basis of UTC offsets is you’d be surprised by how many people have no clue what any of them are. But “Americas” vs “Australia”, they’ll get that right
I suspect a large number of users might choose PST if in California, when they really mean PST/PDT. Or perhaps in the summer they would semi-correctly choose PDT.
Choosing a large city you know shares your time zone does make things a bit more “human“.
Offset alone is not enough because different TZ names also point to different DST schedules (current and historic) and past changes.
You can look at the tz data files to see what that looks like.
I'm curious as to what people in Phoenix would select as their timezone under your proposed solution?
if one is serious, one just chooses UTC.
one can play with timezones all they want, but in the end it's a presentation issue.
Not for events in the future!
When you plan a future event for 5PM on September 2nd 2029 in Latveria, we can guess when that will occur, but don't really know because Dr. Doom could arbitrarily re-zone the country at any time. Or maybe the country won't even exist.
Future events are triggering conditions. Making a prediction and storing your prediction in UTC is a very bad idea, because your prediction might become wrong, and now you have no way to recalculate.
UTC helps store specific moments in time. Notably it does not solve for "dates" nor recurrence. Many of my hairs have been lost to third parties thinking they've created viable systems simply because they use UTC.
Running UTC as a clock on an end user workstation is about the dumbest thing you can do (unless they reside in UTC).
Let's hear why you think this.
Doing this at the system level was one of the better ideas to come out of unix.