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I'm trying to build functions that help me execute frequent sparse tree queries, using org-match-sparse-tree nil "<some_query>" in my code.

Some of these queries need to contain constraints such as SCHEDULED<=<end_of_this_month>, where <end_of_this_month> just means the end of the current month. The same could be true for this week, next week, this year, and so on.

I know about the possibility of writing SCHEDULED<=<1+y>, but that just means 1 year from now, meaning, as of the time of this writing, from Aug 28 2019 to Aug 27 2020, which is not what I want.

Is there a way to, programmatically, obtain in a string the end of the current or next month/year/week without having to manually calculate those (meaning using a preexisting date-handling function)?

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    The calendar.el library has a function: (calendar-last-day-of-month MONTH YEAR). There is probably a buit-in function to obtain the current month / year, but if not, you can extract it form (current-time) and/or format-time-string that defaults to the current time ..... See also org-time-today, parse-time-string and org-parse-time-string ... – lawlist Aug 28 '19 at 21:32
  • See also the elmo.el library that has a function that is easily extracted/separated called elmo-time-to-datevec (which relies on the built-in timezone.el library) -- see github.com/wanderlust/wanderlust/blob/master/elmo/elmo-date.el E.g., (elmo-time-to-datevec (current-time)) at this precise moment in time returns [2019 8 28 14 50 56 (-25200 "PDT")] and we can then extract the nth element from the vector ... – lawlist Aug 28 '19 at 21:50
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    (calendar-last-day-of-month (string-to-number (format-time-string "%m")) (string-to-number (format-time-string "%y"))) – Ivan Perez Aug 28 '19 at 21:52
  • I think that would work. Hmm, I wonder how to get the last day of the current week, now? – Ivan Perez Aug 28 '19 at 21:53
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    Here is a link that contains a function last-day-of-week ... andersen.berlin/emacs.d I have not studied to see who wrote it .... The result is in time and needs to be converted ... – lawlist Aug 28 '19 at 22:01
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Arthur Andersen has published his emacs configuration, and contains exactly these functions, here. (Credit to @lawlist for pointing out where this was, in the comments to the original question.)

The functions to calculate end of the day/month/year are:

(defun last-day-of-year ()
  "Return the last day of the year as time."
  (encode-time 0 0 0 31 12 (nth 5 (decode-time
                                    (current-time)))))

(defun last-day-of-month ()
  "Return the last day of month as time."
  (let* ((now (decode-time (current-time)))
         (month (nth 4 now))
         (year (nth 5 now))
         (last-day-of-month (calendar-last-day-of-month month year)))
        (encode-time 0 0 0 last-day-of-month month year)))

(defun last-day-of-week ()
  "Return the last day of the week as time."
  (let* ((now (current-time))
         (datetime (decode-time now))
         (dow (nth 6 datetime)))
        (time-add now (days-to-time (- 7 dow)))))

These functions return a time, not a date, so you need to convert them appropriately, such as:

(format-time-string "%Y-%m-%d" (last-day-of-year))
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