What is the date of an Aquinox

September 22, 2020: Like a world day - because it is the equinox worldwide

Contents of this page here:

Equinox are the two days of the year on which the light day and night have the same length. “The sun crosses the celestial equator at the equinox, so on this day it is ... at the time of the equinox vertically above the earth's equator. Day and night are then roughly the same length all over the world, "

“The definition is therefore independent of the location of a real observer; the equinoxes occur worldwide at the same point in time, which however corresponds to different times in different time zones. ”wikipedia.

In 2020, on September 22nd at 3:31 p.m. it will be time for the center of the solar disk to cross the celestial equator. This is the case worldwide at the same (real) time. But the time changes from year to year: “Because the average duration of one orbit of the earth around the sun in relation to the spring equinox (tropical year) is about 365.2422 days, almost six hours longer than the duration of the calendar common year with exactly 365 Days, the calendar date of the equinoxes shifts from one common year to the next to a time about six hours later. With the insertion of February 29th in a leap year, the equinox time is around 18 hours earlier than the previous year. ”Wikipedia.


The equinox is the momentwhen the sun crosses the celestial equator during its apparent annual movement on the ecliptic. The points of intersection of the ecliptic and the equator are called the spring and autumn or Aries and Libra points.

Photo: by S.fonsi [CC BY-SA 3.0 or GFDL], via Wikimedia Commons

Advertising: Tips on the equinox

Postcards, a book (99 €!), A BBC documentary and a planetary system

Other astronomical days

March 30th: Not a world day, but nationwide the popular astronomy day

January 7th: Not a world day, but historically almost a day of astronomy

July 5th: No world day but we are in aphelion. And the story of the bikini's birthday is just as untrue as other fake news about July 5th.

CategoriesNature & Environment, Knowledge & Information, Science & Technology