A mod that lets you adjust the length of each of the four phases of the day (dawn, day, dusk, and night).

Each one is specified in seconds, and all separately, so you can make any part as long or short as you want.

Setting a phase to 0 length will disable that phase.

By default, it makes night as long as day without changing any of the other times, but it can easily be set to anything else through the mod settings menu.
If you change the settings in-game, you may need to let the game run for a few moments, and then do a save and load before it will pick up the new numbers.

Forum thread: https://forums.factorio.com/47019

For older versions of Factorio, either manually edit the "info.json" file, or see the forum thread.

Changelog:
v1.0.1 Doesn't freeze time anymore, since it's apparently not needed, and will stay frozen even if the mod is removed.
v1.0.0 Initial release

Uninstallation:
If time stays frozen after removing the mod, you can either enter "/c game.surfaces['nauvis'].freeze_daytime(false)" in the command console, or you can get the TimeUnfreezer from the forum thread, enable it, load the save, save the save, and remove TimeUnfreezer.