Hi Salome,
The decode-time function returns a list that includes the day-of-week as
a number from 0-6. You'll have to give it an encoded time, which you
can use encode-time for.
A wild idea would be to use the shell "date" command, which is overkill
for this, but I just happen to have this code handy, in case you or
anyone else might find it useful:
#+BEGIN_SRC elisp
(defmacro call-process-with-args (process &rest args)
"Return results of running PROCESS with ARGS."
(declare (indent defun))
`(with-temp-buffer
(unless (= 0 (call-process ,process nil t nil
,@args))
(user-error ,(concat process " failed")))
(buffer-substring-no-properties (point-min) (point-max))))
(defun get-day-of-week (string)
"Parse STRING with the shell `date' command and return day-of-week as string."
(call-process-with-args
"date" "-d" string "+%a"))
#+END_SRC
