[tz] [PROPOSED PATCH] Improve guesses for post-2037 Iran

[Paul Eggert]

* NEWS: Document this.
* asia (Iran): Predict 2038 and later DST to be March 21 thru Sept. 21.
This is not correct, but it's better than predicting no DST.
---
 NEWS |  6 ++++++
 asia | 11 +++++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/NEWS b/NEWS
index b4e1483..121e0e4 100644
--- a/NEWS
+++ b/NEWS
@@ -11,6 +11,12 @@ Unreleased, experimental changes
     America/Metlakatla switched from PST all year to AKST/AKDT on
     2015-11-01 at 02:00.  (Thanks to Steffen Thorsen.)
 
+  Changes affecting future time stamps
+
+    Asia/Tehran now has DST predictions for the year 2038 and later,
+    to be March 21 00:00 to September 21 00:00.  This is likely better
+    than predicting no DST, albeit off by a day every now and then.
+
   Changes affecting documentation
 
     tz-link.htm mentions the BDE library (thanks to Andrew Paprocki).
diff --git a/asia b/asia
index 5467024..f170244 100644
--- a/asia
+++ b/asia
@@ -1084,8 +1084,15 @@ Rule	Iran	2032	2033	-	Mar	21	0:00	1:00	D
 Rule	Iran	2032	2033	-	Sep	21	0:00	0	S
 Rule	Iran	2034	2035	-	Mar	22	0:00	1:00	D
 Rule	Iran	2034	2035	-	Sep	22	0:00	0	S
-Rule	Iran	2036	2037	-	Mar	21	0:00	1:00	D
-Rule	Iran	2036	2037	-	Sep	21	0:00	0	S
+#
+# The following rules are approximations starting in the year 2038.
+# These are the best post-2037 approximations available, given the
+# restrictions of a single rule using a Gregorian-based data format.
+# At some point this table will need to be extended, though quite
+# possibly Iran will change the rules first.
+Rule	Iran	2036	max	-	Mar	21	0:00	1:00	D
+Rule	Iran	2036	max	-	Sep	21	0:00	0	S
+
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone	Asia/Tehran	3:25:44	-	LMT	1916
 			3:25:44	-	TMT	1946     # Tehran Mean Time
-- 
2.5.0