[tz] Time Zone Database

EL MAAYATI Afaf afaf at anrt.ma
Wed Mar 22 12:47:42 UTC 2023

Dear Paul,

  Thank you for your prompt feedback.

Please let us know once the fix for 2023 issue is implemented.

Best Regards,


National Telecommunications Regulatory Agency


-----Message d'origine-----
De : Paul Eggert <eggert at cs.ucla.edu>
Envoyé : jeudi 16 mars 2023 19:07
À : EL MAAYATI Afaf <afaf at anrt.ma>
Cc : Naela Sarras <naela.sarras at icann.org>; kim.davies at icann.org; ma <ma at anrt.ma>; Time Zone Mailing List <tz at iana.org>
Objet : Re: Time Zone Database

On 3/16/23 01:26, EL MAAYATI Afaf wrote:

> (https://www.iana.org/time-zones <https://www.iana.org/time-zones>),

> for Africa region, and especially for Morocco, it’s mentioned that a

> program will be running to implement the transition dates.

Yes, I wrote that program to guess what Moroccan authorities will do in the future. Unfortunately, I don't know how to predict what Moroccan authorities will do, atop the underlying well-known uncertainty about when Ramadan will occur.

The program I wrote was conservative: when it wasn't absolutely sure that Ramadan would end by a certain time, it delayed the spring-forward transition by another week. This year Moroccan authorities did not delay similarly - i.e., they were less conservative than I was. Possibly this is because their astronomical calculations are more precise than mine, so that they can afford to be more aggressive in their predictions.

I worked around the 2023 problem by using a more-aggressive calculation as described here:


and this fix should be in the next tzdb release, which should be published soon.

This patch affects spring-forward predictions for 2023, 2031, 2038, 2046, etc. However, it's likely that in the future the tzdb tables will need to be corrected again, as Moroccan authorities' calculation method evidently differs from the one published in tzdb.

If someone could let us know exactly how the Moroccan authorities calculate DST start and end time, we could presumably fix the tzdb calculations to match. This should avoid the need for last-minute corrections and so would make Morocco's clocks more reliable.



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