bug#57803: 28.2; decoded-time-add results in message "obsolete timestamp with cdr 1"

[Gustavo Barros]

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 
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