First day of spring 2023: What to know about the vernal equinox
Here’s some news we can all use: Spring officially begins at 5:24 p.m. EDT on Monday, March 20, ushering in a new season of warmer weather, more sunlight and all the spring changes we look forward to every year.
Spring is not an arbitrary date on the calendar, however. It’s actually the astronomical beginning of a new season, occurring at the moment when the Earth’s axis is tilted neither toward nor away from the sun, resulting in a nearly equal amount of daylight and darkness at all latitudes, according to the National Environmental Satellite and Information Service.
Equinoxes occur twice a year, in March and September. In March it is known as the vernal equinox, with “vernal” deriving from the Latin word for spring, and “equinox” coming from aequus (equal) and nox (night).
All four seasons on our calendars begin with astronomical events: The two equinoxes mark the start of spring and fall, and the solstices, which occur in June and December, are the official beginning of summer and winter.
Interestingly, the Vernal Equinox fell on March 21 during most of the 20th century, but due to the 400-year Gregorian calendar cycle, the event occurs a tiny bit earlier every year, according to the Old Farmer’s Almanac. Due to time zone differences, the Almanac says, there won’t be a March 21 equinox in mainland U.S. during the entire 21st century.
Another fascinating equinox fact: Both the spring and fall equinoxes bring about the chance to witness zodiacal light, a phenomenon that causes an eerie cone of light to appear over the sunrise or sunset point in the fully dark nighttime sky. With the vernal equinox on Monday and a new moon (i.e., very dark skies) on Tuesday, this week would be a great time to try to see it. Learn how here.
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