I'm running Ubuntu 12.04 but I think this was occurring before. If I edit the interval, changing the end time to a later time that is past the present time (so the timer automatically will move to the correct present time), the start time also gets adjusted. For example, say the start time is 15:30 and the end time is 18:24. I adjust the end time to 18:30 (a time ahead of the actual time, which is 18:27). When the timer starts, the end time will be put back to the correct time, 18:27 but the start time will also be put back the same amount of time.