month

There are still some traces of the lunar calendar in the modern calendar

Base data: Time
Long month = 31 days = 2,678,400 sec. Short month = 30 days = 2,592,000 sec. or 28 days = 2,419,200 sec. (February) or 2,505,600 sec. (Leap Year February)

The waxing and waning of the moon takes 29.53 days

The exact number of days is takes for the moon to wax and wane is 29.53. Many races in ancient times adopted the lunar calendar, which arranged the months alternately into 29 and 30 days. The number of days of a month ranges from 28 to 31, which is a holdover from the lunar calendar despite the waxing and waning of the moon having nothing to do with the solar calendar.