In 2020, the spring equinox, also known as the vernal equinox, begins today – Thursday, March 19th. Even though an early spring was predicted on Ground Hog’s Day, this year is certainly special because it is the earliest date for the beginning of spring in more than a century.
This vernal equinox marks the astronomical first day of spring in the Northern Hemisphere. This date also has an impact on when Easter takes place – on the first Sunday, following the first full moon, following the vernal equinox.
For much of the last century, the spring equinox has occurred on March 20 or 21. This year, however, the equinox occurs on the 19th in all time zones in America. The last time spring arrived this early was in 1896 – 124 years ago. Why is the equinox so early this year? It is all based the astronomical orientation of the Earth. 2020 is a leap year and that accounts for part of the reason, but the time of the equinox varies by about six hours each year, due to the actual number of hours in a solar year versus a calendar year. We use a leap year to make up the difference, but it is actually a bit less than six hours, namely by 13 minutes. Over the course of a century, that small difference adds up! How much – well for 2020 it has added up to 27 hours, or a little more than one day since 1896. That is enough to shift us into a March 19th vernal equinox each leap year for the next several cycles.