Tonight at 11:50 spring will officially arrive.
That’s the earliest vernal equinox in 124 years.
The reason has to do with the time it takes the Earth to orbit the Sun and how we keep time with our calendars.
Earth takes 365 days, five hours, 48 minutes and 46 seconds to make its yearly orbit.
Because it isn’t exactly 365 days, we occasionally add a day to the calendar, like we did this year.
This extra day helps keep the calendar in line with seasonal astronomical positions like the equinoxes and the solstices.
The vernal equinox, or first day of spring, can occur on March 19, 20 or 21.
Between the years 2020 and 2048, the equinox will fall on the 19th. All other years, it will happen on the 20th.
The last time the equinox fell on the 21st was in 2007 and it won’t happen again until 2101.