[gerikson]

Can confirm, in my last job we supported customers in Morocco and our software dealt directly with timezones, so it was a ... challenge.

I can't remember the details, but in some countries the only legally acceptable date for the start of Ramadan is the direct observation of the new moon. Thus the day when Ramadan starts cannot be predicted in advance. Note that I believe this is the case mostly in the Gulf states, other Muslim-majority countries are fine to trust astronomical calculations.

[madcaptenor]

It seems like they could declare that the time would change on dates that are safely before Ramadan starts / after Ramadan ends.