Verb
(idiomatic) To go to bed to sleep.
(idiomatic) To cease what one has been doing for the night.
Source: en.wiktionary.orgWe were about to give up and call it a night when somebody threw the girl off the bridge. John D. MacDonald
It's over when you decide it's over," Norah says. "When you call it a night. The rest is just a matter of where the sun is in the sky. That has nothing to do with us. Rachel Cohn