On 2022-03-18 07:14:52 (+0800), Paul Eggert via tz wrote:
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.
The abbreviations are going to be misleading no matter what. It's Malaysian Standard Time according to the National Metrology Institute of Malaysia https://mst.sirim.my. As I pointed out in another thread, I believe we should simply do away with these abbreviations and track only offsets. Overlays such as CLDR could take our "-7" and turn it into "Pacific Time" if they wanted to.
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.
How we model this in tzdb will presumably have to depend on how the final legislation is written. If it ends up being permanent daylight saving, and the definitions of the standard offsets are unchanged, then software will expect the tm_isdst flag to be set. It's worth remembering that politicians assign a rather more flexible definition to the word "permanent" than laymen. I think the modelling of tm_isdst is a completely orthogonal discussion to what the abbreviations end up being. And a much more important one! Philip -- Philip Paeps Senior Reality Engineer Alternative Enterprises