Re: [Emacs-diffs] master 0e56883: Move undocumented time-stamp formats closer to format-time-string

[Paul Eggert <eggert@cs.ucla.edu>]

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On 10/9/19 11:52 AM, Eli Zaretskii wrote:
> Do you understand why macOS returns UTC where GMT is expected?

Yes, it's what the low-level gmtime_r function returns in its struct tm. This 
aspect of gmtime_r is not standardized, and some implementations return "GMT", 
some "UTC", and I vaguely recall seeing other abbreviations.

I installed the attached patch, which should fix the problem though I've tested 
it only on GNU/Linux.

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From a05609991f68de5825b37a9ed6b1e5d2cccbd2ae Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Thu, 10 Oct 2019 00:15:24 -0700
Subject: [PATCH] Port time-stamp-test-time-zone to macOS
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Problem reported by Stefan Kangas in:
https://lists.gnu.org/r/emacs-devel/2019-10/msg00360.html
* test/lisp/time-stamp-tests.el (time-stamp-test-time-zone):
Don’t assume (format-time-string "%Z" 0 t) returns "GMT".
---
 test/lisp/time-stamp-tests.el | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/test/lisp/time-stamp-tests.el b/test/lisp/time-stamp-tests.el
index ace5e58e36..37822f6e29 100644
--- a/test/lisp/time-stamp-tests.el
+++ b/test/lisp/time-stamp-tests.el
@@ -298,12 +298,14 @@ time-stamp-test-day-number-in-week
 (ert-deftest time-stamp-test-time-zone ()
   "Test time-stamp formats for time zone."
   (with-time-stamp-test-env
-    ;; implemented and documented since 1995
-    (should (equal (time-stamp-string "%Z" ref-time) "GMT"))
-    ;; documented 1995-2019
-    (should (equal (time-stamp-string "%z" ref-time) "gmt"))
-    ;; implemented since 1997, documented since 2019
-    (should (equal (time-stamp-string "%#Z" ref-time) "gmt"))))
+    (let ((UTC-abbr (format-time-string "%Z" ref-time t))
+	  (utc-abbr (format-time-string "%#Z" ref-time t)))
+      ;; implemented and documented since 1995
+      (should (equal (time-stamp-string "%Z" ref-time) UTC-abbr))
+      ;; documented 1995-2019
+      (should (equal (time-stamp-string "%z" ref-time) utc-abbr))
+      ;; implemented since 1997, documented since 2019
+      (should (equal (time-stamp-string "%#Z" ref-time) utc-abbr)))))
 
 (ert-deftest time-stamp-test-non-date-conversions ()
   "Test time-stamp formats for non-date items."
-- 
2.17.1