OSTARA (pronounced O-STAR-ah) is one of the Lesser Sabbats and is usually celebrated on the Vernal or Spring Equinox right around March 20/21 (although because of its origins, may instead be celebrated on the fixed date of March 25). Other names by which this Sabbat may be known are Oestara, Eostre’s Day, Rite of Eostre, Alban Eilir, Festival of the Trees, and Lady Day.
Ostara is a time to celebrate the arrival of Spring, the renewal and rebirth of Nature herself, and the coming lushness of Summer. It is at this time when light and darkness are in balance, yet the light is growing stronger by the day. The forces of masculine and feminine energy, yin and yang, are also in balance at this time.
Ravenhawks' Magazine Magick for Mind Body and Soul 