bug#22302: 25.1.50; time-stamp ignores time-stamp-time-zone

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

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On 01/11/2016 08:40 PM, Glenn Morris wrote:
> Harald Hanche-Olsen wrote:
>
>> Run emacs -Q and insert this text:
>> Time-stamp: <>
>>
>> Then do:
>> M-: (require 'time-stamp) RET
>> M-x set-variable RET time-stamp-time-zone RET "UTC" RET
>> M-x time-stamp
>>
>> Expected result: A UTC time stamp is inserted.
>> Actual result: A time stamp in the local time zone is inserted.
> This is due to af32fa956. Paul, could you have a look please?

Thanks for reporting this. I fixed the bug by installing the attached 
patch to emacs-25.

By the way, the value "UTC" is not portable to non-GNU systems, and 
POSIX says that in theory it could cause Emacs to crash. The value 
should be "UTC0" or (in Emacs 25) t. I see that some of Emacs's own 
source files have this issue, and plan to look into that.

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From 92f27b6928b99b75630cda663c4a726c0b8ec0bf Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Tue, 12 Jan 2016 09:09:27 -0800
Subject: [PATCH] Fix time-stamp-time-zone bugs introduced in July

This fixes a bug introduced when the July changes to
format-time-string installed, as the changes were not
correctly handled in this module (Bug#22302).
Also, document time stamp time zones.
* lisp/time-stamp.el (time-stamp-time-zone): Document values better.
(time-stamp--format): New private function.
(time-stamp-string, time-stamp-string-preprocess)
(time-stamp-do-number): Use it.
* doc/emacs/files.texi (Time Stamps): Mention time zones.
* doc/misc/autotype.texi (Timestamps): Document time-stamp-time-zone.
---
 doc/emacs/files.texi   |  7 ++++---
 doc/misc/autotype.texi |  8 +++++---
 lisp/time-stamp.el     | 48 ++++++++++++++++++++++++++----------------------
 3 files changed, 35 insertions(+), 28 deletions(-)

diff --git a/doc/emacs/files.texi b/doc/emacs/files.texi
index bfa55d3..3d5562d 100644
--- a/doc/emacs/files.texi
+++ b/doc/emacs/files.texi
@@ -881,9 +881,10 @@ Time Stamps
 @code{before-save-hook} (@pxref{Hooks}).  When you save the file, this
 function then automatically updates the time stamp with the current
 date and time.  You can also use the command @kbd{M-x time-stamp} to
-update the time stamp manually.  For other customizations, see the
-Custom group @code{time-stamp}.  Note that the time stamp is formatted
-according to your locale setting (@pxref{Environment}).
+update the time stamp manually.  By default the time stamp is
+formatted according to your locale setting (@pxref{Environment}) and
+time zone (@pxref{Time of Day,,, elisp, The Emacs Lisp Reference
+Manual}).  For customizations, see the Custom group @code{time-stamp}.
 
 @node Reverting
 @section Reverting a Buffer
diff --git a/doc/misc/autotype.texi b/doc/misc/autotype.texi
index 839782a..6bdbd34 100644
--- a/doc/misc/autotype.texi
+++ b/doc/misc/autotype.texi
@@ -531,15 +531,17 @@ Timestamps
 customization buffer.
 
 @vindex time-stamp-active
+@findex time-stamp-toggle-active
 @vindex time-stamp-format
-@vindex time-stamp-start
+@vindex time-stamp-time-zone
 The time stamp is updated only if the customizable variable
 @code{time-stamp-active} is on, which it is by default; the command
 @code{time-stamp-toggle-active} can be used to toggle it.  The format of
-the time stamp is set by the customizable variable
-@code{time-stamp-format}.
+the time stamp is set by the customizable variables
+@code{time-stamp-format} and @code{time-stamp-time-zone}.
 
 @vindex time-stamp-line-limit
+@vindex time-stamp-start
 @vindex time-stamp-end
 @vindex time-stamp-count
 @vindex time-stamp-inserts-lines
diff --git a/lisp/time-stamp.el b/lisp/time-stamp.el
index 46c993e..dffd590 100644
--- a/lisp/time-stamp.el
+++ b/lisp/time-stamp.el
@@ -121,9 +121,12 @@ time-stamp-old-format-warn
   :group 'time-stamp)
 
 (defcustom time-stamp-time-zone nil
-  "If non-nil, a string naming the timezone to be used by \\[time-stamp].
-Format is the same as that used by the environment variable TZ on your system."
-  :type '(choice (const nil) string)
+  "The time zone to be used by \\[time-stamp].
+Its format is that of the ZONE argument of the `format-time-string' function,"
+  :type '(choice (const :tag "Emacs local time" nil)
+                 (const :tag "Universal Time" t)
+                 (const :tag "system wall clock time" wall)
+                 (string :tag "TZ environment variable value"))
   :group 'time-stamp
   :version "20.1")
 ;;;###autoload(put 'time-stamp-time-zone 'safe-local-variable 'string-or-null-p)
@@ -412,6 +415,8 @@ time-stamp-toggle-active
 	  (> (prefix-numeric-value arg) 0)))
   (message "time-stamp is now %s." (if time-stamp-active "active" "off")))
 
+(defun time-stamp--format (format time)
+  (format-time-string format time time-stamp-time-zone))
 
 (defun time-stamp-string (&optional ts-format)
   "Generate the new string to be inserted by \\[time-stamp].
@@ -420,8 +425,7 @@ time-stamp-string
   (or ts-format
       (setq ts-format time-stamp-format))
   (if (stringp ts-format)
-      (format-time-string (time-stamp-string-preprocess ts-format)
-                          nil time-stamp-time-zone)
+      (time-stamp--format (time-stamp-string-preprocess ts-format) nil)
     ;; handle version 1 compatibility
     (cond ((or (eq time-stamp-old-format-warn 'error)
 	       (and (eq time-stamp-old-format-warn 'ask)
@@ -515,32 +519,32 @@ time-stamp-string-preprocess
 	  "%%")
 	 ((eq cur-char ?a)		;day of week
 	  (if change-case
-	      (format-time-string "%#a" time)
+	      (time-stamp--format "%#a" time)
 	    (or alt-form (not (string-equal field-width ""))
 		(time-stamp-conv-warn "%a" "%:a"))
 	    (if (and alt-form (not (string-equal field-width "")))
 		""			;discourage "%:3a"
-	      (format-time-string "%A" time))))
+	      (time-stamp--format "%A" time))))
 	 ((eq cur-char ?A)
 	  (if alt-form
-	      (format-time-string "%A" time)
+	      (time-stamp--format "%A" time)
 	    (or change-case (not (string-equal field-width ""))
 		(time-stamp-conv-warn "%A" "%#A"))
-	    (format-time-string "%#A" time)))
+	    (time-stamp--format "%#A" time)))
 	 ((eq cur-char ?b)		;month name
 	  (if change-case
-	      (format-time-string "%#b" time)
+	      (time-stamp--format "%#b" time)
 	    (or alt-form (not (string-equal field-width ""))
 		(time-stamp-conv-warn "%b" "%:b"))
 	    (if (and alt-form (not (string-equal field-width "")))
 		""			;discourage "%:3b"
-	    (format-time-string "%B" time))))
+	    (time-stamp--format "%B" time))))
 	 ((eq cur-char ?B)
 	  (if alt-form
-	      (format-time-string "%B" time)
+	      (time-stamp--format "%B" time)
 	    (or change-case (not (string-equal field-width ""))
 		(time-stamp-conv-warn "%B" "%#B"))
-	    (format-time-string "%#B" time)))
+	    (time-stamp--format "%#B" time)))
 	 ((eq cur-char ?d)		;day of month, 1-31
 	  (time-stamp-do-number cur-char alt-form field-width time))
 	 ((eq cur-char ?H)		;hour, 0-23
@@ -554,27 +558,27 @@ time-stamp-string-preprocess
 	 ((eq cur-char ?p)		;am or pm
 	  (or change-case
 	      (time-stamp-conv-warn "%p" "%#p"))
-	  (format-time-string "%#p" time))
+	  (time-stamp--format "%#p" time))
 	 ((eq cur-char ?P)		;AM or PM
-	  (format-time-string "%p" time))
+	  (time-stamp--format "%p" time))
 	 ((eq cur-char ?S)		;seconds, 00-60
 	  (time-stamp-do-number cur-char alt-form field-width time))
 	 ((eq cur-char ?w)		;weekday number, Sunday is 0
-	  (format-time-string "%w" time))
+	  (time-stamp--format "%w" time))
 	 ((eq cur-char ?y)		;year
 	  (or alt-form (not (string-equal field-width ""))
 	      (time-stamp-conv-warn "%y" "%:y"))
-	  (string-to-number (format-time-string "%Y" time)))
+	  (string-to-number (time-stamp--format "%Y" time)))
 	 ((eq cur-char ?Y)		;4-digit year, new style
-	  (string-to-number (format-time-string "%Y" time)))
+	  (string-to-number (time-stamp--format "%Y" time)))
 	 ((eq cur-char ?z)		;time zone lower case
 	  (if change-case
 	      ""			;discourage %z variations
-	    (format-time-string "%#Z" time)))
+	    (time-stamp--format "%#Z" time)))
 	 ((eq cur-char ?Z)
 	  (if change-case
-	      (format-time-string "%#Z" time)
-	    (format-time-string "%Z" time)))
+	      (time-stamp--format "%#Z" time)
+	    (time-stamp--format "%Z" time)))
 	 ((eq cur-char ?f)		;buffer-file-name, base name only
 	  (if buffer-file-name
 	      (file-name-nondirectory buffer-file-name)
@@ -634,7 +638,7 @@ time-stamp-do-number
 			       (format "%%:%c" format-char)))
     (if (and alt-form (not (string-equal field-width "")))
 	""				;discourage "%:2d" and the like
-      (string-to-number (format-time-string format-string time)))))
+      (string-to-number (time-stamp--format format-string time)))))
 
 (defvar time-stamp-conversion-warn t
   "Warn about soon-to-be-unsupported forms in `time-stamp-format'.
-- 
2.5.0