The First of February belongs to Brigid, (Brighid, Brigit, Bride,) the Celtic goddess who in later times became revered as a Christian saint. Originally, her festival on February 1 was known as Imbolc or Oimelc, two names which refer to the lactation of the ewes, the flow of milk that heralds the return of the life-giving forces of spring. Later, the Catholic Church replaced this festival with Candlemas Day on February 2, which is dedicated to the Virgin Mary and features candlelight processions. The powerful figure of Brigid the Light-Bringer overlights both pagan and Christian celebrations.
Read more here http://www.chalicecentre.net/imbolc.htm