Unpredictably, sometimes when I sync my iTouch the time and date go wonky, and suddenly I'm 12 hours and a month in the past. This wreaks havoc on any chance I had at using the calendar functions, and since I've recently started using a journalling app, it was time to fix it.
Turns out that it's a known bug with no current fix from Apple as of the latest firmware. However, there's a workaround, at least one that's working for me. The problem only happens when iTunes is running and then you plug in your device. If you close iTunes, then plug in the device (and let iTunes launch on detection), I get the right time, every time.
It's a bit of a pain to have to remember that, but not as much as being beeped by reminders of meetings that happened a month ago.