Ostara or Eostre is celebrated on or around March 21st or the Spring Equinox. It is the opposite of Mabon and marks a day with equal hours of night and day and the beginning of spring. It is a day of new beginnings and fertility. Symbols that represent the day are hares and eggs. The holiday was later adapted into Easter. You can work out when Easter Sunday is as it is the first Sunday after the first Full Moon after the Equinox.