What day of the year is as long as night?

1, March 20th or March 2nd of Gregorian calendar1:On the day of the vernal equinox, the sun almost shines directly at the equator of the earth, so the day and night around the world are almost equal, each with 12 hours. The vernal equinox is an important solar term, which not only has astronomical significance: the northern and southern hemispheres are equally divided day and night, but also has obvious characteristics in climate. In ancient times, it was also called "Japan-China", "Day and Night" and "Mid-spring Moon".

2. Gregorian calendar September 22-24: On the day of the autumnal equinox, the sun reaches 180 (autumnal equinox), almost reaching the equator of the earth, and the length of day and night is equal all over the world (regardless of the refraction of the sun light by the atmosphere and the shadow in the morning).

Extended data:

If you refine the spring, summer, autumn and winter, you can get three points each. Spring, divided into Meng Chun, Zhongchun and Ji Chun; Autumn is divided into Qiu Meng, Qiu Zhong and Qiu Ji. Each is divided into one month, ***90 days.

The vernal equinox and autumnal equinox are the 90-day midpoint of the Spring and Autumn Period, hence the name. Summer is also divided into Xia Meng, midsummer and the last month of summer; Winter is also divided into Meng Dong, Midwinter and Ji Dong.

Baidu encyclopedia-autumnal equinox (one of the 24 solar terms)

Baidu encyclopedia-vernal equinox (one of the 24 solar terms)

People's Daily Online-Nanfang Daily: Equinox