I have created simple commands to help gamers who are making a map and dont want it to rain or turn to night while people are playing it. It's a simple contraption that automatically sets the game time to day and at the same time, sets the weather to clear. The mechanism is just a Daylight Sensor, a little bit of redstone, a NOT gate (a block with redstone leading to it and a redstone torch on the opposite side), and two command blocks. These are two ways to build the mechanism, one of which doesn't have the NOT gate, but it has a Redstone Comparator. Some of the Minecraft redstone mechanisms actually work like real-life circuitry, except bigger, and this is a pretty good example of it, except for the command blocks.