The moon or moon phase at the end of the lunar calendar. New moon in the morning; Meniscal insufficiency. The waning moon: the waning moon at the end of the lunar calendar, which is different from the "new moon" at the beginning of the month, is the sign of the end of the lunar calendar. At this time, the moon is not far from the west of the sun, and only a small part of its circular surface is bright. The waning moon and the last quarter moon appear in the eastern sky after dawn and midnight respectively, and their "faces" face the east, that is, the eastern half is bright. The waning moon is like a hook, which is the most vivid description and metaphor of the waning moon. Tang Bai Juyi's poem "The Moon in the Guest": "Dawn follows the waning moon, and the evening follows the new moon." Song Liu Yong's Yulin Order says, "Where will I wake up after drinking tonight? Yang Liuan and Xiaofeng are dying. " Chen Yi's poem "Crossing Weishan Lake": "The shadow of Lunan Peak is very steep, and the waning moon draws a boat." On the first day of each month in the lunar calendar, when the moon moves between the sun and the earth, the moon faces the earth with its dark side and rises and falls with the sun, so people can't see it. At this time, the moon phase is called "new moon" or "new moon". After the new moon, the moon gradually moved out of the area between the earth and the sun. At this time, we began to see that a small part of the moon was illuminated by sunlight and shaped like a curved thin sheet, so the moon phase at this time was called "the waning moon". This "waning moon" can only be seen in the western sky in the evening. By the eighth day of the eighth lunar month, from the perspective of the earth, the moon has moved to 90 degrees east of the sun. At this time, we can see the bright half of the west of the moon. At this time, the moon phase is called "winding". The first quarter moon can only be seen in the first half of the night, and then disappears in the west at midnight. After the first winding, the moon becomes round day by day, and we can see most of the bright hemispheres of the moon. At this time, the moon phase is called "convex moon". On the fifteenth and sixteenth day of the lunar calendar, the moon runs across the celestial sphere to the opposite side of the sun, and the distance between the sun and the moon is 180, that is, the earth is located between the sun and the moon. Seen from the earth, all the light of the moon is directed towards the earth. At this time, the moon phase is called "full moon" or "full moon". The full moon rises in the east at dusk and sets in the west at dawn. After the full moon, the moon becomes thinner and thinner as the position of the sun and the moon approaches. It went through the stages of convex moon, last quarter moon and waning moon in turn, and finally returned to the position of new moon. In China, it is customary to call the waning moon in the second half of the month "waning moon". The first quarter moon and the last quarter moon, the waning moon and the waning moon are similar in appearance, but their appearance time, position and bright surface direction are different. The waning moon and the first quarter moon appear in the western sky in the evening and the first half of the night respectively, and their "faces" are facing west, that is, the western half is bright; The waning moon and the last quarter moon appear in the eastern sky after dawn and midnight respectively, and their "faces" face the east, that is, the eastern half is bright. Because the date of the China lunar calendar is arranged according to the moon phases, the working people in ancient China sometimes rely on it to judge the date of the China lunar calendar and the approximate time of night. It takes an average of 29.53 days for the moon to move from the new moon position to return to the new moon position again, which means that the replacement period of the moon phase is 29.53 days on average, which is called a "new moon".