THE LOWDOWN
You download and install flu.x on your windows PC
At night your adjust flu.x to eliminate blue light from a monitor or laptop screen which is stimulating. Blue light is fine for daytime hours but stimulating at night and messes with your sleep cycles
FLU.X also comes in Apple and Android flavors but I have not installed any of that. Go figure this out yourself. Linux too probably.
On iOS there’s nothing to install, it is just there in the display settings. Set it up for sundown to sunrise is my recommendation.