Ostara is a modern Neopagan festival. It is loosely based on several holidays which were celebrated around the spring equinox. The modern holiday does not have a strong relation to any known historical Pagan religious observation.
In the northern hemisphere, the end of March is the focus for a number of religious and traditional celebrations. As the sun appears to cross the earth’s equator on the 20th or 21st of March, entering the Zodiacal sign of Aries, day and night will be equal in length. This astronomical phenomenon is a day anciently revered amongst Pagan peoples. Their festivals included Alban Elfed, the Teutonic festival in honour of Eostre, Roman Hilaria Matris Deûm, Welsh Gwyl Canol Gwenwynol (‘Day of the Gorse’), the Christian Feast of the Annunciantion of the Virgin Mary (Lady Day) as well as Easter itself. The Wiccan Eostar (Ostara) Sabbat (one of the four lesser Wiccan holidays or sabbats of the Wheel of the Year) is a more recent addition to the Spring time festivities.
Here in the southern hemisphere the spring equinox will fall this year on Tuesday September 23, 2008 at 1:44AM. Many southern hemisphere pagans choose to celebrate Ostara when it is seasonally appropriate, in September, rather than following the northern dates.