in the presence of a large gravitaional mass, time slows down. so the next time you need time all you gotta do is get near a black hole ... you know there was this tribe that measured time by the length of a persons shadow. the tall people would get to meetings early and the short ones would get there late. One particularly obtuse yet tall tribesman was told by another tribesman, "you know, you're a waste of height." (ok, it's a lame joke, ok.)