[tz] [PROPOSED 3/3] tzselect: support POSIX.1-2024 offset range

[Paul Eggert]

* NEWS: Mention this.
* tzselect.ksh (check_POSIX_TZ_string): Support the extended
offset range of POSIX.1-2024, so that users can enter a proleptic
TZ setting like "IST-2IDT,M3.4.4/26,M10.5.0".
---
 NEWS         |  7 ++++---
 tzselect.ksh | 13 +++++++------
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/NEWS b/NEWS
index 8f362cb9..6a2c7398 100644
--- a/NEWS
+++ b/NEWS
@@ -64,9 +64,10 @@ Unreleased, experimental changes
     The SUPPORT_C89 option now defaults to 1 instead of 0, fixing a
     POSIX-conformance bug introduced in 2023a.
 
-    tzselect now assumes POSIX.2-1992 or later, as practical porting
-    targets now all support this.  Also, tzselect uses some features
-    from POSIX.1-2024 if available.
+    tzselect now supports POSIX.1-2024 proleptic TZ strings.  Also, it
+    assumes POSIX.2-1992 or later, as practical porting targets now
+    all support that, and it uses some features from POSIX.1-2024 if
+    available.
 
   Changes to build procedure
 
diff --git a/tzselect.ksh b/tzselect.ksh
index 48159afd..ca3d82c6 100644
--- a/tzselect.ksh
+++ b/tzselect.ksh
@@ -425,7 +425,7 @@ while
     eval '
       doselect '"$quoted_continents"' \
 	"coord - I want to use geographical coordinates." \
-	"TZ - I want to specify the timezone using a POSIX.1-2017 TZ string." \
+	"TZ - I want to specify the timezone using a proleptic TZ string." \
 	"time - I know local time already." \
 	"now - Like \"time\", but configure only for timestamps from now on."
       continent=$select_result
@@ -449,16 +449,17 @@ while
 
   case $continent in
   TZ)
-    # Ask the user for a POSIX.1-2017 TZ string.  Check that it conforms.
+    # Ask the user for a proleptic TZ string.  Check that it conforms.
     check_POSIX_TZ_string='
       BEGIN {
 	tz = substr(ARGV[1], 2)
 	ARGV[1] = ""
 	tzname = ("(<[[:alnum:]+-][[:alnum:]+-][[:alnum:]+-]+>" \
 		  "|[[:alpha:]][[:alpha:]][[:alpha:]]+)")
-	time = ("(2[0-4]|[0-1]?[0-9])" \
-		"(:[0-5][0-9](:[0-5][0-9])?)?")
-	offset = "[-+]?" time
+	sign = "[-+]?"
+	hhmm = "(:[0-5][0-9](:[0-5][0-9])?)?"
+	offset = sign "(2[0-4]|[0-1]?[0-9])" hhmm
+	time = sign "(16[0-7]|(1[0-5]|[0-9]?)[0-9])" hhmm
 	mdate = "M([1-9]|1[0-2])\\.[1-5]\\.[0-6]"
 	jdate = ("((J[1-9]|[0-9]|J?[1-9][0-9]" \
 		 "|J?[1-2][0-9][0-9])|J?3[0-5][0-9]|J?36[0-5])")
@@ -479,7 +480,7 @@ while
       read tz
       $AWK "$check_POSIX_TZ_string" ="$tz"
     do
-      say >&2 "'$tz' is not a conforming POSIX.1-2017 timezone string."
+      say >&2 "'$tz' is not a conforming POSIX proleptic TZ string."
     done
     TZ_for_date=$tz;;
   *)
-- 
2.43.0