November, December and the first month of the lunar calendar can be regarded as the first month, and the first day of each month is the first day of the month. There are three algorithms on the first day of a month, starting from Pindan (the time of dawn), Crow and midnight.

Extended data

The first day of each month in the lunar calendar is the new moon. The moon on the new moon is called the new moon, which is generally invisible. The fifteenth day of each month in the lunar calendar is the full moon. The moon on that day is called the full moon, and its shadow is round. People call the cycle of the new moon and the full moon a new moon.

The end of the month corresponding to the new moon is called a dark day, and when the moon is full, it is called looking at the sun. Because of the method of determining the new moon, the sun may fall on the sixteenth, so there is a saying of "fifteen moons and sixteen circles".

The lunar calendar adopts the method of "fixing the new moon"-taking the new moon as the first day of each month, dividing the tropic year into 24 solar terms, and placing the leap in the month of qi deficiency, which not only reflects the influence of the sun's thermal action on the earth, but also reflects the periodic change of the moon, and the tidal force of the sun on the earth, which is the treasure of China traditional culture.

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