Clock

A Clock is a Redstone-related item which was added in Update 0.8.0. It displays the positions of the Sun and Moon.

Usage
Clocks are used to measure time in Minecraft PE, which is helpful when the player is not paying attention to the Sun, or when they are currently somewhere where the sky isn't visible.

Measuring Time
Time can be measured using Clocks by observing the upper part of it. When it is blue, it is day, whereas when it is black, it is night. Time cannot be measured in the Nether.

Crafting

 * 1 Redstone + 4 Gold Ingots => 1 Clock

Trivia

 * Clocks were added in 0.8.0 when Redstone Ore became mineable.
 * Clocks were one of the few Redstone features added before Update 0.13.0.
 * Clocks, Compasses and Maps are useless in the Nether because they just spin around wildly since there is no time in other dimensions and no proper place to tell where you are.
 * Clocks are similar to a Compass, but Compasses tell direction rather than time.
 * Clocks were useless in the Creative inventory until Update 0.10.0, when day/night cycles were added to Creative Mode.
 * Clocks have a similar crafting recipe to a Compass.
 * The difference is that the Iron Ingots are replaced by Gold Ingots.
 * After waking up from a Bed, the Clock is exactly half-blue and half-black.
 * Similarly, the player can only Sleep once the clock is at least half-blue and half-black, but with the colors reversed when waking up.
 * Clocks only show their time when they are in the hot bar, in the players' hand, and in an Item Frame.