Okay, clock making. Lets make a clock. So this one's nice and easy. You need to make a diamond with four gold nuggets, put one red stone in the middle and there you have a clock. How easy is that? So, as you can see this clock is telling me exactly what time it is. Well, not exactly but it's giving me an idea of what time it is and it's going to go clockwise, obviously. So that little blue and yellow icon is the sun and it's going to turn to the right and then when that is half blue and half black that's going to be dusk and then when it's all black it's going to be midnight. And since it's not so easy to find gold you might not want to waste four golding just to see what time it is if you're down under mining. So a quick way to do this is to check this out. See this clock and see that clock? They are the same so you don't actually have to craft the clock, it's going to tell you what time it is no matter what so if you can just build this and check it and then put the stuff back in your inventory so you don't have to waste it. On the other hand you do have to hang on to them but you might be hanging on to them until you come back above ground anyway.
All right, fancy. So now it's nighttime and I've got my clock here and I know it's nighttime because my clock says so and obviously if you are down here mining then you can't see the sky and you know what time of day it is. And that's pretty much all a clock is good for and that's it.