On Fri, 4 Jan 2019 at 14:43, Deborah Goldsmith via tz <tz@iana.org> wrote:
Here’s the (partial) diff of transitions that results from 2018i vs. 2018g (both generated from rearguard tarballs):
Africa/Casablanca Sun Jun 17 01:59:59 2018 UTC = Sun Jun 17 01:59:59 2018 +00 isdst=0 Africa/Casablanca Sun Jun 17 02:00:00 2018 UTC = Sun Jun 17 03:00:00 2018 +01 isdst=1 -Africa/Casablanca Fri Oct 26 22:59:59 2018 UTC = Fri Oct 26 23:59:59 2018 +01 isdst=1 -Africa/Casablanca Fri Oct 26 23:00:00 2018 UTC = Sat Oct 27 00:00:00 2018 +01 isdst=0 -Africa/Casablanca Mon Jan 18 03:14:07 2038 UTC = Mon Jan 18 04:14:07 2038 +01 isdst=0 -Africa/Casablanca Tue Jan 19 03:14:07 2038 UTC = Tue Jan 19 04:14:07 2038 +01 isdst=0 +Africa/Casablanca Sun May 5 01:59:59 2019 UTC = Sun May 5 02:59:59 2019 +01 isdst=1 +Africa/Casablanca Sun May 5 02:00:00 2019 UTC = Sun May 5 02:00:00 2019 +00 isdst=0
Debbie
The issue seems to have been introduced in ziguard.awk at https://github.com/eggert/tz/blob/8539a448ebc8897e40d62f16dc4d0ada3f07b3ca/z... in 8539a44 <https://github.com/eggert/tz/commit/8539a448ebc8897e40d62f16dc4d0ada3f07b3ca>, which is causing the substitution. Though I will admit it was not straightforward deriving the intent of that substitution from the comments, it is there because the 2018-10-26 transition was NOT a transition in UT offset. In a rearguard sense, 2018g predicted that the new timezone of +01 would be permanent and thus switched to +01 with rearguard isdst=0 on 2018-10-26. As it is now expected that Morocco will "fall back" to +00 each Ramadan, 2018h and 2018i consider rearguard isdst to have instead remained 1 on 2018-10-26 (since there was no clock change), and that the flag will become rearguard isdst=0 when the clocks fall back each Ramadan. (The vanguard format, by contrast, considers +01 the new "standard" time effective 2018-10-26, which would show up as a transition from +01, isdst=1 to +01, isdst=0; and Ramadan is considered to have negative DST.) So the diff you're seeing here, best I can tell, reflects expected behavior and accurate data for Morocco in 2018h and 2018i. -- Tim Parenti