[tz] [PROPOSED] Assume zic 2004 or later in "Apr Sun>=25" etc.

[Paul Eggert]

* asia (Zion), northamerica (Toronto): Use constructs like
"Apr Sun>=25" and "Apr Fri<=1" that have been supported by zic
since 2004.  Although Solaris 8 used pre-2004 zic, Solaris 8
reached end-of-life in March 2012.
* zic.8: State more clearly that "Apr Sun>=25" is allowed.
---
 asia         | 19 +------------------
 northamerica | 17 ++++-------------
 zic.8        |  9 +++++++++
 3 files changed, 14 insertions(+), 31 deletions(-)

diff --git a/asia b/asia
index f97c830..9518756 100644
--- a/asia
+++ b/asia
@@ -1782,32 +1782,15 @@ Rule	Zion	2004	only	-	Sep	22	1:00	0	S
 #
 #	ftp://ftp.cs.huji.ac.il/pub/tz/announcements/2005+beyond.ps
 
-# From Paul Eggert (2012-10-26):
-# I used Ephraim Silverberg's dst-israel.el program
-# <ftp://ftp.cs.huji.ac.il/pub/tz/software/dst-israel.el> (2005-02-20)
-# along with Ed Reingold's cal-hebrew in GNU Emacs 21.4,
-# to generate the transitions from 2005 through 2012.
-# (I replaced "lastFri" with "Fri>=26" by hand.)
-# The spring transitions all correspond to the following Rule:
-#
-# Rule	Zion	2005	2012	-	Mar	Fri>=26	2:00	1:00	D
-#
-# but older zic implementations (e.g., Solaris 8) do not support
-# "Fri>=26" to mean April 1 in years like 2005, so for now we list the
-# springtime transitions explicitly.
-
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
-Rule	Zion	2005	only	-	Apr	 1	2:00	1:00	D
+Rule	Zion	2005	2012	-	Apr	Fri<=1	2:00	1:00	D
 Rule	Zion	2005	only	-	Oct	 9	2:00	0	S
-Rule	Zion	2006	2010	-	Mar	Fri>=26	2:00	1:00	D
 Rule	Zion	2006	only	-	Oct	 1	2:00	0	S
 Rule	Zion	2007	only	-	Sep	16	2:00	0	S
 Rule	Zion	2008	only	-	Oct	 5	2:00	0	S
 Rule	Zion	2009	only	-	Sep	27	2:00	0	S
 Rule	Zion	2010	only	-	Sep	12	2:00	0	S
-Rule	Zion	2011	only	-	Apr	 1	2:00	1:00	D
 Rule	Zion	2011	only	-	Oct	 2	2:00	0	S
-Rule	Zion	2012	only	-	Mar	Fri>=26	2:00	1:00	D
 Rule	Zion	2012	only	-	Sep	23	2:00	0	S
 
 # From Ephraim Silverberg (2013-06-27):
diff --git a/northamerica b/northamerica
index 8e5e351..fce043f 100644
--- a/northamerica
+++ b/northamerica
@@ -1701,19 +1701,10 @@ Rule	Toronto	1922	1923	-	May	Sun>=8	2:00	1:00	D
 # was meant.
 Rule	Toronto	1922	1926	-	Sep	Sun>=15	2:00	0	S
 Rule	Toronto	1924	1927	-	May	Sun>=1	2:00	1:00	D
-# The 1927-to-1939 rules can be expressed more simply as
-# Rule	Toronto	1927	1937	-	Sep	Sun>=25	2:00	0	S
-# Rule	Toronto	1928	1937	-	Apr	Sun>=25	2:00	1:00	D
-# Rule	Toronto	1938	1940	-	Apr	lastSun	2:00	1:00	D
-# Rule	Toronto	1938	1939	-	Sep	lastSun	2:00	0	S
-# The rules below avoid use of Sun>=25
-# (which pre-2004 versions of zic cannot handle).
-Rule	Toronto	1927	1932	-	Sep	lastSun	2:00	0	S
-Rule	Toronto	1928	1931	-	Apr	lastSun	2:00	1:00	D
-Rule	Toronto	1932	only	-	May	1	2:00	1:00	D
-Rule	Toronto	1933	1940	-	Apr	lastSun	2:00	1:00	D
-Rule	Toronto	1933	only	-	Oct	1	2:00	0	S
-Rule	Toronto	1934	1939	-	Sep	lastSun	2:00	0	S
+Rule	Toronto	1927	1937	-	Sep	Sun>=25	2:00	0	S
+Rule	Toronto	1928	1937	-	Apr	Sun>=25	2:00	1:00	D
+Rule	Toronto	1938	1940	-	Apr	lastSun	2:00	1:00	D
+Rule	Toronto	1938	1939	-	Sep	lastSun	2:00	0	S
 Rule	Toronto	1945	1946	-	Sep	lastSun	2:00	0	S
 Rule	Toronto	1946	only	-	Apr	lastSun	2:00	1:00	D
 Rule	Toronto	1947	1949	-	Apr	lastSun	0:00	1:00	D
diff --git a/zic.8 b/zic.8
index 6d893c2..89ea2d9 100644
--- a/zic.8
+++ b/zic.8
@@ -317,6 +317,15 @@ may be abbreviated or spelled out in full.
 There must be no white space characters within the
 .B ON
 field.
+The
+.q <=
+and
+.q >=
+constructs can result in a day in the neighboring month;
+for example, the IN-ON combination
+.q "Oct Sun>=31"
+stands for the first Sunday on or after October 31,
+even if that Sunday occurs in November.
 .TP
 .B AT
 Gives the time of day at which the rule takes effect,
-- 
2.21.0