[tz] Central America Time Zone?

Paul Eggert eggert at cs.ucla.edu
Sat Sep 7 11:31:04 UTC 2019

On 9/4/19 6:57 AM, Rodolfo Quesada Zumbado wrote:
> What would be the procedure to suggest an standardized "Central America" time zone?

tzdb doesn't attempt to prescribe names like "Central Time" or "Central America 
Time" for time zones. It tries only to describes common abbreviations when 
people are writing in English about the locations' timestamps. If you're worried 
about names like "Central Time", you'll need to contact whoever's supplying that 
phrase because it's not us.

The story is more complicated for abbreviations like "CST", where POSIX requires 
some sort of abbreviation. Until 2016 tzdb used alphabetic abbreviations for all 
locations, because POSIX formerly required them. For North and Central America 
we used the US/Canada abbreviations since that was easier. For South America I 
invented abbreviations like "PET" for time in Peru.

Some years after POSIX stopped requiring alphabetic abbreviations, we removed 
the South American inventions and used numeric abbreviations like "-05" instead. 
In contrast, for Mexican timestamps the North American abbreviations seem to be 
in common use in English, so we kept them there.

Central America is on the border. One can find English-language sources that use 
North American phrases or abbreviations, such as "Costa Rica is on Central 
Standard Time" (Costa Rica for Dummies, p. 363) or "Time zone UTC-6 (CST)" 
(Costa Rica: Doing Business, Investing in Costa Rica Guide, p. 11), and one can 
find sources that don't, such as "Time zone UTC-06:00 (UTC-6)" (Costa Rica 
Medical & Pharmaceutical Industry Handbook, p. 9), or sources that waffle, such 
as "Costa Rica is in the same time zone as the Central Standard Zone in the U.S. 
(-06:00 GMT)" (Martindale-Hubble 2003, p. CU-1).

My impression, after a quick look into this with a search engine, is that 
although there is no standard "CST" is reasonably common (maybe even a majority) 
for English-language sources writing about Costa Rica. So I'm somewhat inclined 
to have tzdb continue to "CST" etc. in Central America, if only because it's 
better to leave the database alone unless there's a good argument to change it. 
However, if I'm looking at the wrong sources please let me know.

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