[tz] FW: [Ext] The TZ Coordination

Paul Eggert eggert at cs.ucla.edu
Mon Jun 1 06:40:33 UTC 2020

On 5/31/20 10:25 AM, Matt Johnson-Pint wrote:
> why must the DST transitions align so precisely with Ramadan?  Would it not be sufficient if the dates for the time change were predictable as long as the switch to GMT occurred sometime before the start of Ramadan and the switch back to GMT+1 occurred sometime after?  Is there a political, social, or religious reason why they must be so exactly aligned?

They don't need to align exactly, and they aren't aligned exactly in either
2019c or 2020a. Instead, Morocco approximates Ramadan by doing transitions the
weekend before Ramadan starts and the weekend after it ends. 2019c guessed
weekend brackets around Ramadan that were too tight. I loosened the brackets in
2020a by guesswork, and Milamber's email says that my guesses were not quite
loose enough; hence today's patch.

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