Subject: 28.2; decoded-time-add results in message "obsolete timestamp with cdr 1"

From: Gustavo Barros <[email-masked]>
Date: Wed, 14 Sep 2022 10:42:18 -0300

Hi All,

I'm trying to get some dates subtracted of date parts (months) and using 
`decoded-time-add', `decode-time', and `make-decoded-time', following 
the Elisp manual for the purpose.

In the manual "Time Conversion" section we find the following example 
for the `decoded-time-add' function (I just added the required library):

    (require 'time-date)
    (let ((time (decode-time nil nil t))
          (delta (make-decoded-time :month 2)))
      (encode-time (decoded-time-add time delta)))

Evaluating this, we get the message:

    obsolete timestamp with cdr 1 [2 times]

Being less strict in the decoded time format:

    (let ((time (decode-time))
          (delta (make-decoded-time :month 2)))
      (encode-time (decoded-time-add time delta)))

We get:

    obsolete timestamp with cdr 1 [10 times]

(This was evaluated on an "emacs -Q" session).

I'm not sure if this is a documentation problem, and I just failed to 
find a way to satisfy `decoded-time-add', or if there is an actual 
underlying issue.  I think the latter is the case though.  As we see 
from the above examples, we can reduce the number of issued messages by 
specifying the FORM argument to `decode-time' so that it returns the 
seconds in (TICKS . HZ) form.  I'm somewhat surprised that 
`decoded-time-add' is so picky as to not accept the default return value 
from `decode-time', but I don't know these functions enough to make much 
of a stance about this.  Besides, though I may be missing something, I 
could not find a way to specify (TICKS . HZ) form to 
`make-decoded-time', so that `decoded-time-add' still complains even if 
we use `(decode-time nil nil t)'.

A little side report of what is likely just a typo in the manual.  The 
following example in the same section of the manual for the 
`decode-time' function:

    (setf (decoded-time-year decoded-time)
	  (+ (decoded-time-year decoded-time) 4))

results in:

    let*: Symbol’s value as variable is void: decoded-time

Best regards,
Gustavo.

In GNU Emacs 28.2 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.20, 
cairo version 1.16.0)
 of 2022-09-12 built on gusbrs-laptop
Windowing system distributor 'The X.Org Foundation', version 
11.0.12013000
System Description: Linux Mint 20.3

Configured using:
 'configure --with-mailutils --with-xwidgets --with-native-compilation
 --without-compress-install'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES
NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND THREADS TIFF
TOOLKIT_SCROLL_BARS X11 XDBE XIM XPM XWIDGETS GTK3 ZLIB

Important settings:
  value of $LC_MONETARY: pt_BR.UTF-8
  value of $LC_NUMERIC: pt_BR.UTF-8
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
rfc822 mml mml-sec epa derived epg rfc6068 epg-config gnus-util rmail
rmail-loaddefs auth-source eieio eieio-core eieio-loaddefs
password-cache json map text-property-search mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail
rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils dabbrev comp
comp-cstr warnings rx cl-seq cl-macs cl-extra seq byte-opt gv bytecomp
byte-compile cconv thingatpt time-date subr-x help-fns radix-tree
cl-print debug backtrace help-mode find-func cl-loaddefs cl-lib
iso-transl tooltip eldoc paren electric uniquify ediff-hook vc-hooks
lisp-float-type elisp-mode mwheel term/x-win x-win term/common-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list replace
newcomment text-mode lisp-mode prog-mode register page tab-bar menu-bar
rfn-eshadow isearch easymenu timer select scroll-bar mouse jit-lock
font-lock syntax font-core term/tty-colors frame minibuffer cl-generic
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite emoji-zwj charscript
charprop case-table epa-hook jka-cmpr-hook help simple abbrev obarray
cl-preloaded nadvice button loaddefs faces cus-face macroexp files
window text-properties overlay sha1 md5 base64 format env code-pages
mule custom widget hashtable-print-readable backquote threads
xwidget-internal dbusbind inotify lcms2 dynamic-setting
system-font-setting font-render-setting cairo move-toolbar gtk x-toolkit
x multi-tty make-network-process native-compile emacs)

Memory information:
((conses 16 95129 11029)
 (symbols 48 8286 1)
 (strings 32 24337 1548)
 (string-bytes 1 893757)
 (vectors 16 17978)
 (vector-slots 8 350869 17648)
 (floats 8 40 111)
 (intervals 56 419 0)
 (buffers 992 14))