Tokyo is set in the night time, we wanted to achieve a different mood for this new map. I think it gives nice variation. The day and night cycle is a tricky thing when the day lasts about 8 seconds in game. We will definitely need more time to figure out how to implement something like that with the quality we expect for Cities in Motion.
Well the amount of real hours the day lasts it's not a problem. In SimCity 4 we have day and night cycle and it goes slowly while the date goes fast. So its like a day will last 15 game days and a night another 15 game days. Doesn't matter. Pizza Connection 2 also have day/night cycle. It's very nice and accuracy is the least of your problems. I think the hardest is to implement rush hours, or at least something like more visitors to the cinema in the night, more visitors to the golf club during the day. Although, CiM is very dynamic. A person can go out of work and go to the Golf Club instead of home, so it's no strict like SC4. Anyway, just day/night cycle is enough.
Would be nice to see this in the future, especially that in the map editor there are so many options for lights.
Also the map editor should include something to toggle to night view, so you can see if your city is well illuminated before playing.