Sundown

Sundown is a small menu bar app for the Mac that schedules screen warmth. You set it once and the display warms at sunset by itself, which means the screen stops looking like an office at noon while you are reading in bed or finishing work late. How warm it gets is up to you, on a Kelvin ladder that runs from 6500K, plain daylight white, down to 500K, a deep red for very late work, in 100K steps. Everything lives in one small panel in the menu bar, so there is no window to keep open. It runs on macOS 14 or later and it is made by Jack Richards. The site also keeps a page called Screen flicker and eye strain research, which goes through the published studies and is plain about where the evidence is thin.