I just realized how much I hate VXA. Anyways, I finished it. Honestly, besides making sure you have convincing screen tone from the Tint Screen option throughout the time, you should really consider using graphics to control some of that. Tint is great, but you can get more done with images.
I threw in just a black image at 50 transparency and it made it pretty dark during the night cycle.
Try mimicking the normal real life day/night pattern. I made it a 1/60th of a 24 hour system. Sunsets can happen quickly, dawn has weird lighting, night can have beautiful sunsets, but how do you portray that with just tint?
Play with it I guess!