March 21st is the common date of the March equinox (although astronomically the equinox is more likely to fall on March 20 in all but the most easterly longitudes). 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.
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. Yippee only another 279 Days until Christmas.. lol