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“ “Time Difference” (“Zeitverschiebung”) lists time zones for cities etc. – for example, the time zone for San Francisco is America/Los_Angeles.” Does anyone k

“ “Time Difference” (“Zeitverschiebung”) lists time zones for cities etc. – for example, the time zone for San Francisco is America/Los_Angeles.” Does anyone know how the canonical cities/regions associated with a time zone were determined? It seems kind of arbitrary. Wouldn’t “America/California” or “America/Sacramento, CA” make more sense?

roywiggins 5y ago
There is also US/Pacific, which is just an alias for America/Los_Angeles. America/California is ambiguous, because there are several Californias in the "America" area, which encompasses North and South America. https://en.wikipedia.org/wiki/Tz_database#Location https://en.wikipedia.org/wiki/Tz_database#Location > Country names are not used in this scheme, primarily because they would not be robust, owing to frequent political and boundary changes. The names of large cities tend to be more permanent... > Usually the most populous city in a region is chosen to represent the entire time zone, although another city may be selected if it are more widely known, and another location, including a location other than a city, may be used if it results in a less ambiguous name. Basically: globally, regions and countries change, but cities are much slower to change. They don't just pick up and move like borders can.
Groxx 5y ago
AFAIK the common case is that it's just "whatever is in ICU/CLDR", there is no "standard". And I've seen them renamed many times - OS versions don't always agree with each other, for example, much less different OSes.
deleted 5y ago
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x1798DE 5y ago
The full theory on how the names are selected is here: https://www.ietf.org/timezones/tzdb-2021a/theory.html#naming https://www.ietf.org/timezones/tzdb-2021a/theory.html#naming For most zones, it's the largest city in a region where the timekeeping has been the same since 1970. This can cross state or national boundaries.

roywiggins 5y ago

There is also US/Pacific, which is just an alias for America/Los_Angeles. America/California is ambiguous, because there are several Californias in the "America" area, which encompasses North and South America. https://en.wikipedia.org/wiki/Tz_database#Location https://en.wikipedia.org/wiki/Tz_database#Location > Country names are not used in this scheme, primarily because they would not be robust, owing to frequent political and boundary changes. The names of large cities tend to be more permanent... > Usually the most populous city in a region is chosen to represent the entire time zone, although another city may be selected if it are more widely known, and another location, including a location other than a city, may be used if it results in a less ambiguous name. Basically: globally, regions and countries change, but cities are much slower to change. They don't just pick up and move like borders can.

Groxx 5y ago

AFAIK the common case is that it's just "whatever is in ICU/CLDR", there is no "standard". And I've seen them renamed many times - OS versions don't always agree with each other, for example, much less different OSes.

deleted 5y ago

[deleted]

x1798DE 5y ago

The full theory on how the names are selected is here: https://www.ietf.org/timezones/tzdb-2021a/theory.html#naming https://www.ietf.org/timezones/tzdb-2021a/theory.html#naming For most zones, it's the largest city in a region where the timekeeping has been the same since 1970. This can cross state or national boundaries.