When did the days get shorter?

The date is uncertain, but it is usually in the autumn equinox. On the day of the autumnal equinox, the sun reaches the longitude 180 (autumnal equinox), almost pointing to the equator of the earth, and the length of day and night is equal all over the world. After the autumnal equinox, the direct point of the sun continues to move from the equator to the southern hemisphere, and the days in the northern hemisphere become shorter and the nights become longer, that is, the days in a day are shorter than the nights. The southern hemisphere is the opposite.

Introduction:

The autumnal equinox is the sixteenth solar term among the twenty-four solar terms and the fourth solar term in autumn. Fight refers to unitary; The sun reaches the yellow meridian180; Celebrated on September 22-24 of the Gregorian calendar every year. On the day of the autumnal equinox, the sun shines almost directly on the equator of the earth, and the length of day and night is equal all over the world.

The autumnal equinox means "equally divided" and "equally divided", which means equally dividing autumn except day and night. After the autumnal equinox, the position of direct sunlight moves south, and the days in the northern hemisphere become shorter, the nights become longer, the temperature difference between day and night increases, and the temperature drops day by day.