[tz] 2013g - Morocco

[Paul Eggert]

On 10/03/13 09:51, yoshito_umaoka at us.ibm.com wrote:

> For me, above GMT offset transition looks really weird.

It is weird, but the question is how much judgment we should use when
guessing the future.  In the latest experimental version, the
transitions predicted for 2038 are:

   Sun Mar 28 01:59:59 2038 UT = Sun Mar 28 01:59:59 2038 WET isdst=0
   Sun Mar 28 02:00:00 2038 UT = Sun Mar 28 03:00:00 2038 WEST isdst=1

   Thu Sep 30 01:59:59 2038 UT = Thu Sep 30 02:59:59 2038 WEST isdst=1
   Thu Sep 30 02:00:00 2038 UT = Thu Sep 30 02:00:00 2038 WET isdst=0

   Sat Oct 30 01:59:59 2038 UT = Sat Oct 30 01:59:59 2038 WET isdst=0
   Sat Oct 30 02:00:00 2038 UT = Sat Oct 30 03:00:00 2038 WEST isdst=1

   Sun Oct 31 01:59:59 2038 UT = Sun Oct 31 02:59:59 2038 WEST isdst=1
   Sun Oct 31 02:00:00 2038 UT = Sun Oct 31 02:00:00 2038 WET isdst=0

This predicts that Morocco will observe DST during just a one-day
period, from October 30 to October 31, because Ramadan ends on the
30th (thus restoring DST) and the DST-end period is October 31 (thus
reverting to standard time).  Which is pretty weird -- will Moroccans
really change their clocks twice in two days?  So it's tempting to
omit the last two transitions.  But let's look at 2022:

   Sun Mar 27 01:59:59 2022 UT = Sun Mar 27 01:59:59 2022 WET isdst=0
   Sun Mar 27 02:00:00 2022 UT = Sun Mar 27 03:00:00 2022 WEST isdst=1

   Sun Apr  3 01:59:59 2022 UT = Sun Apr  3 02:59:59 2022 WEST isdst=1
   Sun Apr  3 02:00:00 2022 UT = Sun Apr  3 02:00:00 2022 WET isdst=0

   Tue May  3 01:59:59 2022 UT = Tue May  3 01:59:59 2022 WET isdst=0
   Tue May  3 02:00:00 2022 UT = Tue May  3 03:00:00 2022 WEST isdst=1

   Sun Oct 30 01:59:59 2022 UT = Sun Oct 30 02:59:59 2022 WEST isdst=1
   Sun Oct 30 02:00:00 2022 UT = Sun Oct 30 02:00:00 2022 WET isdst=0

This predicts that Moroccans will change their clocks twice in 8 days.
Not as weird, but still pretty weird, and it's tempting to omit the
first two transitions.  But then the question is, where does one stop
omitting transitions?

The answer to this question depends on how much of a stickler
Moroccans will be for following the rules, and that involves complex
religious-commercial-political tradeoffs that I don't pretend to
understand.  In the current experimental version I didn't omit any of
the predicted transitions, as that was one less thing for me to worry
about, but if there's consensus to omit them if they would imply
moving the clocks less than N days apart we can do that too.