Can be boosted quickly with a couple of mods.
Go to the Steam workshop, and subscribe to these two mods.https://steamcommunity.com/sharedfiles/filedetails/?id=15675...https://steamcommunity.com/sharedfiles/filedetails/?id=81469...
"Achieve it" allows you to unlock achievements with mods enabled, and "Time Warp" will let you speed up the day/night cycle by x128.
Once installed, go to the options page in the main menu, and make sure that both mods are enabled.
Start a new, blank city. When Time Warp is enabled, there will be a clock icon added in the bottom left corner, next to the globe and progress buttons. Open the clock menu, and set the day cycle speed to x128. Then set the game speed to x3.
Each day cycle should now only take a few seconds.