For creating Zim wiki pages, I need to generate a timestamp that ends with a time zone in ±hh:mm format. format-time-string has a %z format string that can insert it without the colon. Right now I use with-temp-buffer to generate the timestamp using %z, moving point back two characters and inserting a colon. My question is, is there a more sophisticated way to do this?

3 Answers 3


I'm afraid Emacs is rubbish at string manipulation, which is pretty amazing since Emacs is a text editor. It may not be awesome, but personally feel this reads better than using with-temp-buffer.

(let ((time (format-time-string "%z")))
    (substring time 0 3)
    (substring time 3)))
  • 1
    This feels a bit better for me than @kaushalmodi's regex solution. I actually generalized this in an insert-string-to-string defun. Feb 16, 2015 at 18:45
  • 1
    I think Emacs is actually great for string manipulation, provided you use the buffer type and not the string type. ;-)
    – mbork
    Feb 16, 2015 at 22:23
  • 1
    I agree, but using a buffer to manipulate a 6 characters long string sounds a bit like overkill to me… Feb 18, 2015 at 12:45

If you like to use elisp regexp, you can do the below.

For example, it returns "-05:00" if (format-time-string "%z") returns "-0500".

(replace-regexp-in-string "\\([-+][0-9]\\{2\\}\\)\\([0-9]\\{2\\}\\)"
                          (format-time-string "%z"))
  • Sigh... if only Emacs supported PCRE or something similar without extensions... +1 anyway for the more general text manipulation idea.
    – PythonNut
    Feb 16, 2015 at 18:38

A slightly less verbose version of the one suggested by kaushalmodi:

(replace-regexp-in-string "..$" ":\\&" (format-time-string "%z"))

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