I would say clocks. Because only the noobs who hide in a dirt hut at night but don't have any wool for a bed. Only got a clock from a village. They are the people who use clocks. I just run around at night getting xp
yeah, it is a waste of time, the whole point of it is that you learn how to learn... it's weird but true. Like do you really need information on who the first Primeminister was???