This Year’s Spring Equinox is The Earliest of Our Lifetime

2016 is a leap year. But did you know that this year’s extra day in February could affect the timing of the official first day of spring?

Typically, the March equinox occurs on the 20th or 21st. This year, however, it will occur at 11:30PM CDT on March 19th. Why? It all goes back to the creation of the Gregorian calendar. On this calender, recall that years that are divisible by four are leap years. However, if a year is also divisible by 100, it isnota leap year.

The exception to this rule are years that are divisible by 400. These years do have an extra day in February. So, at the turn of the century, in the year 2000, we had a leap year.

This extra day offset the arrival of the spring equinox for the entire 21st century by about three-quarters of a day early. This, coupled with the extra day in 2016, caused this year’s spring equinox to be the earliest one in about 120 years. In 2020, our next leap year, the equinox will arrive even earlier, and in 2024, spring will come even earlier than that.

By 2100, because the year is divisible by 100 but not 400, the leap year will actually besuppressed.As a result, the March equinox time will be delayed by about one-quarter of a day, causing the first day of spring to return to the 20th of March for the 22nd century.