Computing Days Until with Emacs

08 Apr 2026 Charles Choi

A recent Mastodon post showing the days until the next U.S. election got me to wonder, “how can I compute that in Emacs?” Turns out, this is trivial with the Org mode function org-time-stamp-to-now doing the timestamp computation for you.

We can wrap org-time-stamp-to-now in an internal function cc/--days-until that generates a formatted string of the days until a target date.

(defun cc/--days-until (target &optional template)
  "Formatted string of days until TARGET.

- TARGET: date string that conforms to `parse-time-string'.
- TEMPLATE : format string that includes ‘%d’ specifier.

If TEMPLATE is nil, then a predefined format string will be
used."
  (let* ((template (if template
                       template
                     (concat "%d days until " target)))
         (days (org-time-stamp-to-now target))
         (msg (format template days)))
    msg))

From there we can then start defining commands that use cc/--days-until. The command cc/days-until shown below will prompt you with a date picker to enter a date. Note that you can enter a date value (e.g. “Dec 25, 2026”) in the mini-buffer prompt for org-read-date.

(defun cc/days-until (arg)
  "Prompt user for date and show days until in the mini-buffer.

Use `org-read-date' to compute days until to display in the mini-buffer.

If prefix ARG is non-nil, then the computed result is stored in the
 `kill-ring'."
  (interactive "P")
  (let* ((target (org-read-date))
         (msg (cc/--days-until target)))
    (if arg
        (kill-new msg))
    (message msg)))

Going back to the original motivator for this post, here’s an implementation of days until the next two major U.S. election dates with the command cc/days-until-voting.

(defun cc/days-until-voting (arg)
  "Days until U.S. elections in 2026 and 2028.

If prefix ARG is non-nil, then the computed result is stored in the
 `kill-ring'."
  (interactive "P")
  (let* ((midterms (cc/--days-until "2026-11-03" "%d days until 2026 midterms"))
         (election (cc/--days-until "2028-11-07" "%d days until 2028 presidential election"))
         (msg (format "%s, %s" midterms election)))
    (if arg
        (kill-new msg))
    (message msg)))

The result of M-x cc/days-until-voting as of 8 April 2026 is:

209 days until 2026 midterms, 944 days until 2028 presidential election

It’s so human to want to know how long it’s going to take. Feel free to build your own countdown clocks using the code above. May your journey to whatever you plan be a happy one!

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Computing Days Until with Emacs