celestial-mode-line

Screenshot: 5 days to full moon, sunset at 16:12.

Quick start

Install celestial-mode-line from melpa.

Set your coordinates, so that sunrise/sunset can be calculated correctly.

(setq calendar-longitude 25.5)
(setq calendar-latitude 17.5)
(setq calendar-location-name "Some place")

Add celestial-mode-line-string to the mode line, for example:

;; add to end of global-mode-string
(if (null global-mode-string)
    (setq global-mode-string '("" celestial-mode-line-string))
  (add-to-list 'global-mode-string 'celestial-mode-line-string t))

Start the timer, to update every few minutes:

(celestial-mode-line-start-timer)

If you don’t like the default icons, just set alternatives, any unicode characters should work:

(defvar celestial-mode-line-phase-representation-alist '((0 . "○") (1 . "☽") (2 . "●") (3 . "☾")))
(defvar celestial-mode-line-sunrise-sunset-alist '((sunrise . "☀↑") (sunset . "☀↓")))