Peep of day is a poetic and old-fashioned expression for the time just before dawn, when the first light of the sun starts to appear on the horizon. There are several synonyms for this term that can be used in different contexts. A common alternative is "crack of dawn," which signifies the moment when the sun is just about to rise. "Daybreak" is another synonym that refers to the time when the daylight starts to appear, while "dawn" is a more general term that encompasses the entire period of transition from night to day. Other alternatives include "sunrise," "morning twilight," "first light," and "cockcrow," which is the time when the rooster crows at the start of the day.