Synonyms: vernal or spring equinox
It is the point at which the Sun crosses the celestial equator from South to North on its apparent path around the Earth. It is equivalent to zero degrees of Aries in the tropical zodiac. The other point of intersection is the autumnal equinox which is located directly opposite.
It was called the Aries point because at the time it was named it occurred in the constellation of Aries. Owing to the precession of the zodiac, the Aries point now occurs in the constellation of Pisces. However, this is irrelevant for Western astrology which is based on the tropical zodiac - as opposed to Indian astrology (also known as vedic astrology) which continues to work with the sidereal zodiac.
When the Sun reaches the Spring Equinox around the 21st March, the number of daylight hours is equal all over the globe.
The International Astrology Day is observed on this date.