[tz] [PATCH] Estimate Morocco 2013-2038 transitions for Ramadan.

[Paul Eggert]

Here's a proposed patch to try to address the problem with Moroccan DST.
I've pushed this to the unofficial github version of the tz database.
===
* africa (Morocco): Use GNU Emacs 24.3 to estimate Ramadan-based
DST transition dates for 2013-2038.  Heads-up by Erik Homoet in
<http://mm.icann.org/pipermail/tz/2013-February/018680.html>.
---
 africa | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 54 insertions(+), 1 deletion(-)

diff --git a/africa b/africa
index f378cc4..5f4f8eb 100644
--- a/africa
+++ b/africa
@@ -846,6 +846,41 @@ Zone	Indian/Mayotte	3:00:56 -	LMT	1911 Jul	# Mamoutzou
 # 3:00 am Friday, July 20, 2012 and will again be advanced by 60 minutes
 # August 20, 2012 from 2:00 am.
 
+# From Paul Eggert (2013-03-06):
+# Morocco's daylight-saving transitions due to Ramadan seem to be
+# announced a bit in advance.  On 2012-07-11 the Moroccan government
+# announced that year's Ramadan daylight-saving transitions would be
+# 2012-07-20 and 2012-08-20; see
+# <http://www.mmsp.gov.ma/fr/actualites.aspx?id=288>.
+#
+# To estimate what the Moroccan government will do in future years,
+# transition dates for 2013 through 2021 were determined by running
+# the following program under GNU Emacs 24.3:
+#
+# (let ((islamic-year 1434))
+#   (while (< islamic-year 1444)
+#     (let ((a
+#	     (calendar-gregorian-from-absolute
+#	      (calendar-islamic-to-absolute (list 9 1 islamic-year))))
+#	    (b
+#	     (calendar-gregorian-from-absolute
+#	      (calendar-islamic-to-absolute (list 10 1 islamic-year)))))
+#	(insert
+#	 (format
+#	  (concat "Rule\tMorocco\t%d\tonly\t-\t%s\t %2d\t 3:00\t0\t-\n"
+#		  "Rule\tMorocco\t%d\tonly\t-\t%s\t %2d\t 2:00\t1:00\tS\n")
+#	  (car (cdr (cdr a))) (calendar-month-name (car a) t) (car (cdr a))
+#	  (car (cdr (cdr b))) (calendar-month-name (car b) t) (car (cdr b)))))
+#     (setq islamic-year (+ 1 islamic-year))))
+#
+# with the results hand-edited for 2020-2022, when the normal spring-forward
+# date falls during the estimated Ramadan.
+#
+# From 2023 through 2038 Ramadan is not predicted to overlap with
+# daylight saving time.  Starting in 2039 there will be overlap again,
+# but 32-bit time_t values roll around in 2038 so for now do not worry
+# about dates after 2038.
+
 # RULE	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
 
 Rule	Morocco	1939	only	-	Sep	12	 0:00	1:00	S
@@ -871,10 +906,28 @@ Rule	Morocco	2010	only	-	May	 2	 0:00	1:00	S
 Rule	Morocco	2010	only	-	Aug	 8	 0:00	0	-
 Rule	Morocco	2011	only	-	Apr	 3	 0:00	1:00	S
 Rule	Morocco	2011	only	-	Jul	 31	 0	0	-
-Rule	Morocco	2012	max	-	Apr	 lastSun 2:00	1:00	S
+Rule	Morocco	2012	2019	-	Apr	 lastSun 2:00	1:00	S
 Rule	Morocco	2012	max	-	Sep	 lastSun 3:00	0	-
 Rule	Morocco	2012	only	-	Jul	 20	 3:00	0	-
 Rule	Morocco	2012	only	-	Aug	 20	 2:00	1:00	S
+Rule	Morocco	2013	only	-	Jul	  9	 3:00	0	-
+Rule	Morocco	2013	only	-	Aug	  8	 2:00	1:00	S
+Rule	Morocco	2014	only	-	Jun	 29	 3:00	0	-
+Rule	Morocco	2014	only	-	Jul	 29	 2:00	1:00	S
+Rule	Morocco	2015	only	-	Jun	 18	 3:00	0	-
+Rule	Morocco	2015	only	-	Jul	 18	 2:00	1:00	S
+Rule	Morocco	2016	only	-	Jun	  7	 3:00	0	-
+Rule	Morocco	2016	only	-	Jul	  7	 2:00	1:00	S
+Rule	Morocco	2017	only	-	May	 27	 3:00	0	-
+Rule	Morocco	2017	only	-	Jun	 26	 2:00	1:00	S
+Rule	Morocco	2018	only	-	May	 16	 3:00	0	-
+Rule	Morocco	2018	only	-	Jun	 15	 2:00	1:00	S
+Rule	Morocco	2019	only	-	May	  6	 3:00	0	-
+Rule	Morocco	2019	only	-	Jun	  5	 2:00	1:00	S
+Rule	Morocco	2020	only	-	May	 24	 2:00	1:00	S
+Rule	Morocco	2021	only	-	May	 13	 2:00	1:00	S
+Rule	Morocco	2022	only	-	May	  3	 2:00	1:00	S
+Rule	Morocco	2023	max	-	Apr	 lastSun 2:00	1:00	S
 
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone Africa/Casablanca	-0:30:20 -	LMT	1913 Oct 26
-- 
1.7.11.7