(display-time-world-list): Test for zoneinfo support.

lisp/ChangeLog

+2007-10-30  Jason Rumney  <jasonr@gnu.org>
+
+	* time.el (display-time-world-list): Test for zoneinfo support.
+
 2007-10-30  Michael Albinus  <michael.albinus@gmx.de>
 
 	* net/tramp.el (tramp-maybe-open-connection): Set $LC_ALL to "C".

lisp/time.el

@@ -150,9 +150,17 @@ LABEL is a string to display as the label of that TIMEZONE's time."
   :version "23.1")
 
 (defcustom display-time-world-list
-  (if (memq 'system-type '(gnu/linux ms-dos))
-      zoneinfo-style-world-list
-    legacy-style-world-list)
+  ;; Determine if zoneinfo style timezones are supported by testing that
+  ;; America/New York and Europe/London return different timezones.
+  (let (gmt nyt)
+    (set-time-zone-rule "America/New York")
+    (setq nyt (format-time-string "%z"))
+    (set-time-zone-rule "Europe/London")
+    (setq gmt (format-time-string "%z"))
+    (set-time-zone-rule nil)
+    (if (string-equal nyt gmt)
+        legacy-style-world-list
+      zoneinfo-style-world-list))
   "Alist of time zones and places for `display-time-world' to display.
 Each element has the form (TIMEZONE LABEL).
 TIMEZONE should be in the format supported by `set-time-zone-rule' on