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(Caveat that this may be US specific.) For the Central time zone there are 2 variants. CST and CDT. Most people will wrongly use CST to mean both variants but t

(Caveat that this may be US specific.) For the Central time zone there are 2 variants. CST and CDT. Most people will wrongly use CST to mean both variants but that is incorrect. Central Standard Time only applies when daylight savings is off and Central Daylight Time only applies when it is on. The same is true for say PST and PDT.

mdavidn 5y ago
CST and CDT are known as a single time zone, America/Chicago, in the tz database. The tz database can convert UTC times into local Chicago time. It even accommodates historic changes in DST law, like changes to the start date in prior years.
tshaddox 5y ago
It's common to casually refer to "CST" and "CDT" as "time zones." I was only pointing out that in the specific context of the tz database, "time zone" has a specific definition that is distinct from individual UTC offsets.
- jrockway 5y ago
  Yeah. CST is a sloppy term; your computer is going to be America/Chicago or America/Indiana/Indianapolis (for the weird one that doesn't use DST), and those are unambiguous. (While researching this comment, I found that Indiana has at least 8 different time zones, so ... good luck with that.) I don't know if you can type things like "CST" into Debian, but I don't think you can.
  - jcranmer 5y ago
    > (While researching this comment, I found that Indiana has at least 8 different time zones, so ... good luck with that.) This is kind of the weakness with the IANA time zone classification. This defines time zones as the set of clocks that have shared the same time since 1970, so every time an Indiana county decided it wanted to move from Eastern to Central or vice versa, it got split into its own timezone. It reflects a level of precision that is perhaps greater than Indianans themselves actually keep. [Also, FWIW, Indiana does observe DST now.]
  - LukeShu 5y ago
    > CST is a sloppy term; It's not though, it means "Central Standard Time", which is UTC-06:00. It is sometimes sloppily misused to mean "Central Time", which is a sloppy term, meaning either UTC-06:00 (CST) or UTC-05:00 (CDT) depending on the time of year and where you are in the country. > or America/Indiana/Indianapolis (for the weird one that doesn't use DST) 1. You mean `America/Indiana/Knox` or `America/Indiana/Tell_City` or historically almost any of the other `America/Indiana/…` zoneinfo files except for Indianapolis. Indianapolis has "always" (since 1961) been "Eastern" rather than "Central", it's other non-Indianapolis regions of Indiana that have been "Central, but without DST". 2. But regardless, it's outdated; all of Indiana has been doing DST since 2006; mostly Eastern (EDT/EST), but a few western parts of the state are Central (CDT/CST). > (While researching this comment, I found that Indiana has at least 8 different time zones, so ... good luck with that.) They only still exist for pre-2007 dates; for post-2007 dates they're all equivalent to either America/Chicago (…/Knox and …/Tell_City) or America/New_York (the other 6 of them). > I don't know if you can type things like "CST" into Debian, but I don't think you can. It's inconsistent. You can type in EST or MST, but not CST.
nineteen999 5y ago
East Coast of Australia is similiar - normally we are AEST (Australian Eastern Standard Time), but during daylight savings, we are in AEDT (Australian Eastern Daylight Savings Time).
- Jedd 5y ago
  A taxonomy that's frustrating for a separate reason - the majority of the Australian east coast does not use DST. (That's if you go by length of coast. If you go by population of states that do use DST, then, okay. If you go by number of states with a coast on the eastern side of the country that use DST, that's only 2/3, or 3/4 if you include Tasmania.)
  - abryzak 5y ago
    Also I recently noticed that DuckDuckGo time zone conversion ignores you when you enter AEST and uses AEDT when the other states are in daylight savings time and yours is not.
  - nineteen999 5y ago
    Yeah, I was only referring to the Eastern states that do use DST at all. But thanks for pointing that out, although it might just have been clearer to say that Queensland does not use DST.

mdavidn 5y ago

CST and CDT are known as a single time zone, America/Chicago, in the tz database. The tz database can convert UTC times into local Chicago time. It even accommodates historic changes in DST law, like changes to the start date in prior years.

tshaddox 5y ago

It's common to casually refer to "CST" and "CDT" as "time zones." I was only pointing out that in the specific context of the tz database, "time zone" has a specific definition that is distinct from individual UTC offsets.

jrockway 5y ago
Yeah. CST is a sloppy term; your computer is going to be America/Chicago or America/Indiana/Indianapolis (for the weird one that doesn't use DST), and those are unambiguous. (While researching this comment, I found that Indiana has at least 8 different time zones, so ... good luck with that.) I don't know if you can type things like "CST" into Debian, but I don't think you can.
- jcranmer 5y ago
  > (While researching this comment, I found that Indiana has at least 8 different time zones, so ... good luck with that.) This is kind of the weakness with the IANA time zone classification. This defines time zones as the set of clocks that have shared the same time since 1970, so every time an Indiana county decided it wanted to move from Eastern to Central or vice versa, it got split into its own timezone. It reflects a level of precision that is perhaps greater than Indianans themselves actually keep. [Also, FWIW, Indiana does observe DST now.]
- LukeShu 5y ago
  > CST is a sloppy term; It's not though, it means "Central Standard Time", which is UTC-06:00. It is sometimes sloppily misused to mean "Central Time", which is a sloppy term, meaning either UTC-06:00 (CST) or UTC-05:00 (CDT) depending on the time of year and where you are in the country. > or America/Indiana/Indianapolis (for the weird one that doesn't use DST) 1. You mean `America/Indiana/Knox` or `America/Indiana/Tell_City` or historically almost any of the other `America/Indiana/…` zoneinfo files except for Indianapolis. Indianapolis has "always" (since 1961) been "Eastern" rather than "Central", it's other non-Indianapolis regions of Indiana that have been "Central, but without DST". 2. But regardless, it's outdated; all of Indiana has been doing DST since 2006; mostly Eastern (EDT/EST), but a few western parts of the state are Central (CDT/CST). > (While researching this comment, I found that Indiana has at least 8 different time zones, so ... good luck with that.) They only still exist for pre-2007 dates; for post-2007 dates they're all equivalent to either America/Chicago (…/Knox and …/Tell_City) or America/New_York (the other 6 of them). > I don't know if you can type things like "CST" into Debian, but I don't think you can. It's inconsistent. You can type in EST or MST, but not CST.

nineteen999 5y ago

East Coast of Australia is similiar - normally we are AEST (Australian Eastern Standard Time), but during daylight savings, we are in AEDT (Australian Eastern Daylight Savings Time).

Jedd 5y ago
A taxonomy that's frustrating for a separate reason - the majority of the Australian east coast does not use DST. (That's if you go by length of coast. If you go by population of states that do use DST, then, okay. If you go by number of states with a coast on the eastern side of the country that use DST, that's only 2/3, or 3/4 if you include Tasmania.)
- abryzak 5y ago
  Also I recently noticed that DuckDuckGo time zone conversion ignores you when you enter AEST and uses AEDT when the other states are in daylight savings time and yours is not.
- nineteen999 5y ago
  Yeah, I was only referring to the Eastern states that do use DST at all. But thanks for pointing that out, although it might just have been clearer to say that Queensland does not use DST.