Minecraft wiki entry for Command_blocks_and_functions, associated text: Command blocks and functions can be used, among many other things, to change the difficulty, change the state of the weather, or give a player predesignated items. They are particularly useful for the /weather and /time set commands, as they are only available in cheat mode otherwise. The /time set command is especially useful, as it allows players to change the current time to a preset time at the press of a button.