[tz] Unfortunate time zone names in the United States

Paul Eggert eggert at cs.ucla.edu
Thu Mar 17 23:14:52 UTC 2022

On 3/17/22 14:31, Chris Walton via tz wrote:
> Yukon recently did the same thing.

When Yukon did that, we modeled that as America/Whitehorse and 
America/Dawson being on -07 standard time all year, with the 
abbreviation "MST". This made sense, as that's what "MST" means 
elsewhere in North America.

This new change, if it becomes law, won't be so easy to deal with. It 
will likely cause "Pacific Time" to be synonymous with -07 and "Mountain 
Time" to be synonymous with -06 in popular usage, which means that the 
entries for America/Whitehorse and America/Dawson will need to change 
from "MST" to something else, as "MST" will be misleading.

It's been longstanding tzdb practice to model permanent DST as standard 
time. Admittedly this practice has so far been employed only for 
locations like Argentina that have fewer users. Still, the precedent is 
there and is consistent with the traditional meaning of standard time.

There's another issue here: permanent DST is more likely to break 
software applications. For example, permanent DST in California that is 
called "PDT" and is 7 hours behind Greenwich would entail a POSIX-style 
TZ string like TZ='XXX6PDT7,0/0,J365/23' that means "California's 
standard time is 6 hours behind Greenwich, but it springs backward to 7 
hours behind Greenwich on January 1 at 00:00 and springs forward on 
December 31 at 23:00, so it's actually on daylight saving time all 
year". I suspect these oddball TZ strings would break applications, and 
I doubt whether this approach would be wise even if it barely conforms 
to the standards.

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