旦 means 'dawn'

Rock around the clock with these four kanji. They might seem to represent mere points in a 24-hour stretch. But as 午 appears in terms for "morning" and "afternoon," it applies to a large chunk of the day. Then 宵 takes over, generally meaning "early evening" but also sometimes "evening." We find 更 in terms for the ancient Chinese system of night watches that ran from about 7 p.m. to 5 a.m. Night ends with dawn (旦). These multipurpose kanji also symbolize parts of the year, from New Year's (旦) to late autumn (更).