Question

I’m doing a bit of programming here and there in Emacs Lisp, but I’m not entirely sure how to go about certain things.

I’m trying to insert a whole month of dates, each on a new line like the list below:

January

01/01/09 Mon:

02/01/09 Tue:

03/01/09 Wed:

etc

How would I go about doing that? I’ve found how to format dates, but I can’t find how to loop over a certain range of dates (in this instance to loop round a whole month and print a date for each day in the month).

Has anyone got some pointers they could give me on how to get started?

Answer 1

The functions you want are 'encode-time, 'format-time-string, and 'decode-time. For the proper documentation, either C-h f function-name or will give you the documentation for the function, or the general elisp info pages can be found here: C-h i m elisp RET m time conversion RET

Here’s that snippet:

(defun my-insert-dates ()   'insert a bunch of dates'   (interactive)   (let* ((month 3)          (day 1)          (time (encode-time 1 1 0 day month 2009)))     (while (= (nth 4 (decode-time time)) month)       (insert (format-time-string '%D %a:\n' time))       (setq day (1+ day))       (setq time (encode-time 1 1 0 day month 2009))))) 

I couldn’t find how to determine the number of days in a given month (sure, you could hard-code it, but then you’ve got to deal with leap years). Luckily, 'encode-time does all the addition for you, so if you pass it the equivalent of ‘February 31’, it’ll return ‘March 3’ (assuming 28 days).