[tz] FW: [Ext] The TZ Coordination

Florian Weimer fw at deneb.enyo.de
Sun May 31 11:09:03 UTC 2020

* Paul Eggert:

> On 5/30/20 7:00 AM, Florian Weimer wrote:
>>> Would this be a good opportunity to engage with the government of Morocco
>>> to encourage them to give more warning?
>> My understanding is that at present, they don't know themselves in
>> advance.
> Yes, I think you're right.
>> They would have to redefine the criteria to something based
>> exclusively on astronomical calculations
> That shouldn't be necessary, as they're using a conservative
> approximation; that is, it's OK if their approximation is a bit off
> because all they need to do is to bracket the actual Ramadan rather
> than predict its Gregorian dates exactly.  If they had an algorithm
> they could publish it and we could use it. And it would be
> technically feasible for them to have an algorithm; see the
> Morocco-prediction code in the tzdb 'africa' file for an example
> algorithm.

It looks like the algorithm predicted correctly the data of Eid
al-Fitr as 24 May, but the derivation of the end date from that is
suspicious.  I think it would make more sense if the time change does
not happen on Eid itself.  A rule like this would ensure that Eid
still uses the same time as Ramadan in every year, which is likely
what people expect.

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