This year's equinox is March 19 — the earliest it's happened since 1896
Spring is coming early this year but the reason has nothing to do with a certain groundhog. This year's equinox in the U.S. is March 19, marking the earliest spring in 124 years, according to the Old Farmers' Almanac.
Spring equinox always marks the start of a new season, but it doesn't always land on the same day. From now on, it's going to come earlier and earlier.
The vernal equinox is occurring almost 18 hours ahead of its occurrence in 2019. The last time it fell on March 19, rather than 20 or 21, in the U.S. was 1986.
The Old Farmers' Almanac said the Northern Hemisphere will welcome spring at 11:50 p.m. ET on Thursday, March 19. On that day, both hemispheres receive nearly the same amount of daylight.
During the equinox, the Earth's axis will align perfectly perpendicular to the Sun's rays, transitioning to spring in the Northern Hemisphere and fall in the Southern. The equinoxes are only two times of the year when the Earth's axis is tilted neither toward nor away from the sun.
The complicated reasons for 2020's earlier equinox involve leap years, centuries and the length of time it takes Earth to revolve around the sun.
In the Gregorian calendar, leap years follow specific rules
- Every year that is not divisible by 4 has 365 days
- Every year divisible by 4 has 366 days
- Century years only get a February 29 if they are divisible by 400
The number of days in a year and the number of days in a season are not even. It takes the Earth 365.25 days to orbit the sun and there are 92.771 days in spring, 93.641 in summer, 89.834 in autumn and 88.994 days in winter, according to the Old Farmers' Almanac.
The addition of leap years keeps the astronomical calendar in-sync with the human-created one. Typically, leap years are skipped on century years, but in 2000 — a century year divisible by 400 — February 29 was kept on the calendar.
Because the year 1900 did not have a leap year but the year 2000 did, equinoxes in the 20th century were always on March 20 or 21, but they have now reverted back to March 19.
According to the Old Farmer's Almanac, there will be a new "record earliest" start of spring every leap year from now until 2103, when it will once again occur on March 21 in the U.S.