Within a fraction of a minute a month. Have had it since 2000 but have adjusted it only a couple times. My daily watch is a Raymond Weil, Tango model. It's pretty close to that time, now. Had a basic Casio digital for running, years ago. Lasted a decade and was off only occasionally. That thing would survive anything. Misplaced it, at some point. Best $16.95 watch ever made.