I have a timer going on my iPhone since August 2009. I've gotten 2 new iphones since then-- the stopwatch data gets saved along with backups. Pretty sure it just calculates how many seconds have elapsed since you set it, when you bring up the stopwatch so it's not always calculating it or something. I'm pretty sure what you're seeing here is an integer overflow. Somebody smarter than me can probably tell you exactly how long ago you set the stopwatch.