At first I thought my watch was a dud. This is a self-winding watch powered by wrist movement (not battery) and the self-winding mechanism needs to be primed. Since the watch shipped without any instructions, it took me a while to figure this out. See seller's comment below. You must turn the winding stem at least 40 times to prime the mechanism. Do this when you first receive the watch, and repeat any time it slows or stops due to insufficient wrist movement. If I take the watch off at bedtime then I often have to wind it again in the morning. After that it keeps good time all day.