For runners: any way to calibrate an inaccurate Garmin 305?

Tweet

I have a Garmin 305 running watch that has gotten pretty inaccurate over the last number of months. At first it seemed to show my pace/mileage accurately, then it got wonky, showing me as running much faster than I actually was. I've run a number of races in which it always shows me getting to the mile splits earlier than they appear, which makes the device useless in determining my actual pace, mileage, times, etc. Anyone know if a Garmin 305 or other Garmin watch can be reset or recalibrated or whatever, to get it back to its original accuracy? Thanks!