High Quality Content by WIKIPEDIA articles! March 21 is the 80th day of the year (81st in leap years) in the Gregorian calendar. There are 285 days remaining until the end of the year. In the Northern Hemisphere, meteorological Spring starts on 20 March. In the Southern Hemisphere, meteorological Autumn starts on this date. In astrology, the day of the equinox is the first full day of the sign of Aries. It is also the traditional first day of the astrological year.