Imbolc is one of the four greater Sabbats, celebrated on February 2nd. It is to celebrate the first stirrings of spring from the depths of winter. This is when the first buds can be seen appearing on trees, when the days are quite visibly longer than they were around Yule, and when there are the first days of semi-bearable temperatures. The word Imbolc literally means "In Milk." This is because it is the time when the cows and goats generally begin lactating in Western Europe.
The festival is sacred to the Goddess Brigid (pronounced "Breed, " often spelled "Brid"-the Celtic triple Goddess of Inspiration, Healing, and Metalwork. As well, she is a patroness of midwives (in much the same way as Hecate was to the Hecats in Greece) indeed, the Christianized version of Brid, " St. Brigid", was said to have been Jesus' midwife (and when Brid was occasionally stomped on by the patriarchy, it was said that she was Jesus' maid when he was schooled by the Druids)