[tz] Unexpected last transition in Africa/Casablanca

Paul Eggert eggert at cs.ucla.edu
Tue Mar 22 15:15:30 UTC 2022

On 3/22/22 05:40, Almaz Mingaleev wrote:
> Here are the last transitions in Africa/Casablanca output (rearguard
> format):
> transition,type,[UTC time],[Type offset],[Type isDST]
> 3672612000,1,2086-05-19T02:00:00Z,PT1H,DST
> 3699828000,2,2087-03-30T02:00:00Z,PT0S,STD
> 3703456800,3,2087-05-11T02:00:00Z,PT1H,STD
> So change is from standard to standard, even though offset changes from 0h
> to 1h. Is that expected behaviour?

Yes, as tzdb frowns on permanent daylight saving time for reasons 
discussed recently.

This issue occurs due to the rearguard format's contortion of post-2018 
Morocco data to pretend that standard time is daylight saving and vice 
versa. Even with that contortion, we don't want the normal post-2087 
prediction (standard time only) to be contorted into a rearguard 
post-2087 prediction of daylight saving only.

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