>>> "TP" == Thomas Plass <thunk2@arcor.de> writes:

   > Hello,
   > Uwe Brauer wrote at 09:58 on August 18, 2019:
   > : I sometimes need to insert a date-stamp which corresponds to one month
   > : in a year, say march 2019. I usually insert 
   > : <2019-03-01 Fri>--<2019-03-31 Sun>, but this is cumbersome to do
   > : manually.

   > This'll put the computed result on the kill ring.  Beautification and
   > error checking of input values left as an exercise for the reader.

   > (defun Brauer/make-month-timerange (year month)
   >   (interactive
   >    (list (string-to-int (read-string "Year: " (int-to-string (nth 5 (decode-time)))))
   >          (string-to-int (read-string "Month: " (int-to-string (nth 4 (decode-time)))))))
   >   (let* ((last-day (calendar-last-day-of-month month year))
   >          (start (list 0 0 0 1 month year))
   >          (end (list 0 0 0 last-day month year))
   >          (ts (format "<%d-%02d-%02d %s>--<%d-%02d-%02d %s>"
   >                      year month 1 (format-time-string "%a" (apply #'encode-time start))
   >                      year month last-day (format-time-string "%a" (apply #'encode-time end)))))
   >     (message (substitute-command-keys (concat "Use \\[yank] to yank " ts)))
   >     (kill-new ts)))

Very cool, thanks a lot. But why no

(defun Plass/make-month-timerange (year month)
  (interactive
   (list (string-to-int (read-string "Year: " (int-to-string (nth 5 (decode-time)))))
         (string-to-int (read-string "Month: " (int-to-string (nth 4 (decode-time)))))))
  (let* ((last-day (calendar-last-day-of-month month year))
         (start (list 0 0 0 1 month year))
         (end (list 0 0 0 last-day month year))
         (ts (format "<%d-%02d-%02d %s>--<%d-%02d-%02d %s>"
                     year month 1 (format-time-string "%a" (apply #'encode-time start))
                     year month last-day (format-time-string "%a" (apply #'encode-time end)))))
    (insert ts)))