When is the date of the moon phase?

First quarter moon: The moon continues to rotate forward. On the eighth day of the seventh lunar month, that is, position 3 in the picture, the longitude difference is 90. The sun went down and the moon was already overhead. It didn't fall until midnight. At this time, just half of the moon illuminated by the sun is displayed in front of you. This is the so-called "first quarter moon".

Full Moon: On the 15th and 16th day of the lunar calendar, the moon turns to the other side of the earth, that is, position 5 in the figure, with longitude difference of 180. At this time, the earth is between the sun and the moon, and the half moon illuminated by the sun is just facing the earth. At this time, we see the full moon, or "looking". Because the moon is just opposite to the sun, the sun sets in the west and the moon rises in the east. When the moon sets, the sun rises in the east, and you can see the bright moon all night.

First quarter moon: After the full moon, the moon rises later every day, and the bright part of the moon gets smaller every day. By the 23rd day of the lunar calendar, which is position 7 in the figure, the longitude of the Yellow River is 270. The full moon is half lost, and then half a moon only appears in the eastern sky in the middle of the night, which is the "lower chord".

Near the end of the month, the moon will rotate between the earth and the sun again, and the waning moon will rise in the east shortly before sunrise. On the first day of next month, it is a new moon, and a new cycle begins.

Moon phase is an astronomical term. ?

It is the name of the part of the moon that is illuminated by the sun as seen from the earth. As the moon moves a long distance from east to west in the starry sky every day, its shape is constantly changing, which is the phase change of the moon, called the moon phase.

The moon revolves around the earth, so the relative positions of the sun, the earth and the moon change regularly within a month. Because the moon itself is not luminous and opaque, the visible part of the moon is the part that reflects sunlight. Only the part of the moon that is directly illuminated by the sun can reflect sunlight. We see the part of the moon that is directly illuminated by the sun from different angles, which is the source of the moon phase.