On 1/8/20 11:49 AM, Andrew Lyon wrote:
It appears that many use the tz database as a source of truth.
Ouch. As we say in big letters, "The tz code and data are by no means authoritative." <https://data.iana.org/time-zones/tz-link.html#changes>
I understand there were 10 years between 1930 and 1941 when the hour of Spring daylight saving transition was 0000 (midnight) to 0100. I would like to confirm these entries are in the tz database.
Yes, tzdb says the 10 years 1930/1934 and 1937/1941 all did that, as can be seen from the extract Brian emailed.
I have numerous references that daylight saving time was also observed in America/Regina during world war ONE ( 1914-1918) and I am uncertain if those entries are in the tz database or the hour of those transitions.
As Brian mentioned, tzdb has these two transitions for 1918: Sun Apr 14 08:59:59 1918 UT = Sun Apr 14 01:59:59 1918 MST Sun Apr 14 09:00:00 1918 UT = Sun Apr 14 03:00:00 1918 MDT Sun Oct 27 07:59:59 1918 UT = Sun Oct 27 01:59:59 1918 MDT Sun Oct 27 08:00:00 1918 UT = Sun Oct 27 01:00:00 1918 MST However, there's a good chance these data entries are incomplete for Regina. It's also possible that the entries for 1930/1941 are wrong. For details, please read the commentary for Regina in the northamerica file. Here's the current development version: https://github.com/eggert/tz/blob/master/northamerica