f.lux
Available at https://justgetflux.com/
It adjusts the screen color over the course of the day, suppressing the blue from dusk to dawn. This better mimics natural light and keeps the excess blue from messing with your circadian rhythm. (Blue and UV light tells your brain it's still daytime).
Got it yesterday, slept VERY well last night. Maybe coincidence or placebo effect, but still...
Oh, it’s FREE, too!
This is neat-—thank you!