Minor fixes/simplifications to time functions

* doc/lispintro/emacs-lisp-intro.texi (Files List): Simplify.
* doc/lispref/os.texi (Time of Day): Mention format-time-string
as an alternative to current-time-string.
* lisp/arc-mode.el (archive-unixdate, archive-unixtime):
Port better to future versions of Emacs where (COUNT . HZ)
will take precedence to (HI . LO).
* lisp/arc-mode.el (archive-unixtime):
* lisp/calendar/todo-mode.el (todo-insert-item--basic)
(todo-item-done, todo-read-time):
Prefer format-time-string to substringing current-time-string.
* lisp/calc/calc-forms.el (calc-time, calcFunc-now):
Prefer decode-time to parsing the output of current-time-string.
* lisp/emacs-lisp/cl-extra.el (cl--random-time):
Prefer encode-time to hashing the output of current-time-string.
* lisp/gnus/gnus-score.el (gnus-score-headers)
(gnus-score-adaptive):
Avoid stringifying and then reparsing timestamp.
* src/timefns.c (Fencode_time): Omit redundant assignment.

2 files changed, 5 insertions, 4 deletions

diff --git a/doc/lispintro/emacs-lisp-intro.texi b/doc/lispintro/emacs-lisp-intro.texi
index 0b0c0a167d9..1a1518b2c51 100644
--- a/doc/lispintro/emacs-lisp-intro.texi
+++ b/doc/lispintro/emacs-lisp-intro.texi
@@ -15599,7 +15599,7 @@ like this:
    (recursive-lengths-list-many-files
     (files-in-below-directory "/usr/local/src/emacs/lisp/"))
    '<)
-  (insert (format "%s" (current-time-string))))
+  (insert (current-time-string)))
 @end ignore
 
 @node Counting function definitions
diff --git a/doc/lispref/os.texi b/doc/lispref/os.texi
index 41753859e50..60697f2e29f 100644
--- a/doc/lispref/os.texi
+++ b/doc/lispref/os.texi
@@ -1313,9 +1313,10 @@ This function returns the current time and date as a human-readable
 string.  The format does not vary for the initial part of the string,
 which contains the day of week, month, day of month, and time of day
 in that order: the number of characters used for these fields is
-always the same, so you can reliably
-use @code{substring} to extract them.  You should count
-characters from the beginning of the string rather than from the end,
+always the same, although (unless you require English weekday or
+month abbreviations regardless of locale) it is typically more
+convenient to use @code{format-time-string} than to extract
+fields from the output of @code{current-time-string},
 as the year might not have exactly four digits, and additional
 information may some day be added at the end.