On Nov 24, 2008, at 9:31 PM, Alan E. Davis wrote:

> Thank you for the reply.
>
> On Mon, Nov 24, 2008 at 8:30 PM, Carsten Dominik <dominik@science.uva.nl 
> > wrote:
> Why would you want to turn off the clock?  It is actually
> not running, only a starting time is recorded.  Just "start"
> it again when you need a new clock.
>
> Perfect!  Thank you.
>
>> A further suggestion is born or my initial experiment with his  
>> function: I started the clock a bit too late, so all the timestamps  
>> are off by about 30-40 seconds.  Is it (at least in theory)  
>> possible to adjust all time stamps in a subtree by the same  
>> amount?  That would enable me to correct all of my notes in one  
>> fell stroke.
>
> Of course this is possible, but code for that would need to be  
> written.
>
>
> I have written some elisp, not alot.  May I request a clue where to  
> start?

Well write a function searching for the strings and change them... :-)

Something like this (untested) might do it.  These functions
handle negative times, so you can also use this to change
the timings relative to the beginning of a scene, so that a prelude
to a scene might be at negative times.....:

(defun my-change-times-in-region (beg end delta)
   "Change all h:mm:ss time in region by a DELTA."
   (interactive "r\nsEnter time difference like \"-1:08:26\" or  
\"0:00:25\": ")
   (let ((re "[-+]?[0-9]+:[0-9]\\{2\\}:[0-9]\\{2\\}")
	(delta (my-hms-to-secs delta))
	old new p)
     (when (= delta 0) (error "No change"))
     (save-excursion
       (goto-char end)
       (while (re-search-backward re beg t)
	(setq p (point))
	(replace-match
	 (save-match-data
	   (my-secs-to-hms (+ (my-hms-to-secs (match-string 0)) delta)))
	 t t)
	(goto-char p)))))

(defun my-hms-to-secs (hms)
   "Convert h:mm:ss string to an integer time.
If the string starts with a minus sign, the integer will be negative."
   (if (not (string-match
	    "\\([-+]?[0-9]+\\):\\([0-9]\\{2\\}\\):\\([0-9]\\{2\\}\\)"
	    hms))
       0
     (let* ((h (string-to-int (match-string 1 hms)))
	   (m (string-to-int (match-string 2 hms)))
	   (s (string-to-int (match-string 3 hms)))
	   (sign (equal (substring (match-string 1 hms) 0 1) "-")))
       (setq h (abs h))
       (* (if sign -1 1) (+ s (* 60 (+ m (* 60 h))))))))

(defun my-secs-to-hms (s)
   "Convert integer S into h:mm:ss.
If the integer is negative, the strig will start with \"-\"."
   (let (sign m h)
     (setq sign (if (< s 0) "-" "")
	  s (abs s)
	  m (/ s 60) s (- s (* 60 m))
	  h (/ m 60) m (- m (* 60 h)))
     (format "%s%d:%02d:%02d" sign h m s)))

HTH

- Carsten


Hmmm, looks useful to me also for general note taking, maybe
I can add something linke this to Org....