The main feature of the lunar calendar is that the length of the calendar month is determined according to the astronomical phenomena, that is, the phase of the moon, and the average length of the calendar month is roughly the same as that of Wang Shuoyue. 5306 days, etc. The length of a year is only an integer multiple of a calendar month, which has nothing to do with the tropical year. Therefore, the month of the lunar calendar has nothing to do with the four seasons. The date of the lunar calendar indicates a certain moon phase, that is, the first day is the new moon, that is, the new moon; The fifteenth, sixteenth or seventeenth is the full moon, which means hope; The seventh and eighth days are the first quarter moon; Twenty-two and twenty-three are the last quarter moons, and it is very convenient for the ancients to judge the date by the phase of the moon. The change of the moon phase is the easiest astronomical phenomenon to see, so most of the calendars in various countries have the lunar calendar first and then the solar calendar. However, because the lunar calendar has nothing to do with the tropical year, it is not harmonious with agricultural production and people's daily life, and it was gradually eliminated. Today, except for a few Islamic countries that still use a lunar calendar called "hijri" for religious reasons, all other countries have given up.
In addition,. 19 12 after China adopted the Gregorian calendar to arrange the months, people called it the Gregorian calendar, while the traditional summer calendar coexisting with the people was popularly called the lunar calendar.