Gtimelog is very simple. It provides no method of editing the log of how your time was spent.
Fortunately the program’s simplicity extends to its system files, which encourage easy manual editing, without the need for a separate interface for doing so. The file format of log files benefits from some explanation however.
In Gtimelog click File -> Edit timelog.txt to view the log for the current day. Each task has only one time associated with it, and that is the time that the task ended. The time that any given task started is taken from the end of the preceeding task.
2012-06-15 09:00: Start
2012-06-15 12:00: Eating mailing list spam
2012-06-15 13:00: **Lunch
In the above timelog.txt, the eating of spam commenced at 09.00, and ended at 12.00.