Clock

Clocks work like compasses, in the sense that you cannot use them to change the physical world, but their image changes depending on the circumstances. The clock displays the sun and the moon's position relative to the horizon.

Clocks were added in the Halloween Update on October 31, 2010.

Crafting
Clocks are created by using one redstone dust and four gold ingots (see formation below).

Telling the time
Below is a gif showing how the clock works. The clock consists of two halves with a day side and a night side. These spin slowly to tell you the time of day, corresponding to what is at the top most point.



Alternatives
If you do not have a clock, you can approximate the time by looking at the position of the Sun or Moon in the sky. When underground, or in an area without a view of the sky, you can use the sounds of nearby enemies as a cue to the current time; if you hear the sounds of skeletons or zombies taking damage, you can assume it's dawn, and they are on fire.

In the menu, the item statistics list shows an accurate clock next to your clock statistics.

Furthermore, one quick trick to tell the current time while underground is to toggle the view distance in the options menu. Doing this redraws all blocks around you, which may give you just enough time to see if the sun or moon is out. You may also try mining a long tunnel, of 2 blocks high and 1 block wide, and looking down it from a distance with the shortest view distance selected (in the options menu). You should notice how the lighting in the hallway will become a lighter whitish color during the daytime, and will be a darker blue hue during the night. This technique will work at any level in the earth. Also if you are building some place high (Tower mountain cave roof etc.) you can build a 1x1 tower by jumping and placing blocks, put torches on it and you can tell when its noon or midnight dawn or dusk by the tower. It is also used to find your way back to base. Remember to make the time tower or obelisk taller than the trees.

Textures
Unlike most items the clock combines 2 textures, one being the actual clock, and the other, the dial. So you may change the clock's texture without worrying about breaking the dial, as long as you do not change the transparency.

Future
Notch has said that he is considering the possibility of placing clocks on blocks. It is however unknown if this feature is still planned.

Trivia

 * When switching Anaglyph mode on or off in the options menu, the clock face will appear purple or bright pink respectively when either in the hot bar or held.
 * When the recipe for a clock is laid out on a crafting table, the clock displayed in the output field will be functional; thus you can tell the time without permanently crafting the gold and redstone into a clock.
 * Just like a Compass, Clocks do not work in The Nether or The End. No matter what container it's in, it will turn in any direction randomly at varying speeds, as if it was broken. The clock will work again once the player returns to the Overworld.
 * Unlike most tools, clocks are stackable. This makes multiple clocks easier to store.
 * As with the compass, once one has crafted a clock at any point in any world it is not necessary (although still convenient) to do so again, as the image in the statistics menu is functional.
 * A Clock will function whether it is in your inventory, in a chest, about to be crafted, on the ground, in the statistics menu, in someone else's hand, or anywhere else, even if it is not supposed to be there.