Jane's watch gains ten minutes a day, while Mary's watch loses ten minutes a day. Jane can put up with her watch, but Mary seems to be tired of hers....
Jane: My watch always gains ten minutes a day.
Mary: That's funny. My watch always loses ten minutes a day.
Jane: No kidding.
Mary: I'm serious. Every morning I set my watch by the radio, but it still loses ten minutes.
Jane: You know what you can do?
Mary: Throw it away and buy a new one?
Jane: No, you don't have to. You only need to put your watch back ten minutes everyday.
Mary: So you put your watch back ten minutes everyday?
Jane: Yeah, that's what I'm doing.
Mary: Why bother? Just buy a new watch. It doesn't cost much.
Besides, I just can't put up with this thing any more.