Northern Hemisphere: March 20th-23rd
Southern Hemisphere: September 20th-23rd
Ostara, also known as Eastra.
Little is known about this goddess except that her festival was celebrated at the Spring Equinox and she was the Goddess of fertility by the Northern Europeans. When the Christianized Romans invaded, they turned this time into Easter. The Christian tradition still follows the moon however. Easter is celebrated the first Sunday after the first full moon after the spring equinox!