lights-out
From Longman Dictionary of Contemporary Englishlights-outˈlights-out noun [uncountable] SLEEPthe time at night when a group of people who are in a school, the army etc must put the lights out and go to sleepExamples from the Corpuslights-out• After lights-out we'd all get up and play with this planchette thing.• Their coach plans their days, from wake-up calls to lights-out.