Imbolc — Old Irish, possibly from i mbolg ("in the belly") referring to the pregnancy of ewes, or from imb-fholc ("to wash oneself") referring to purification — is one of the four principal festivals of the ancient Irish calendar, marking the beginning of spring. It falls halfway between the winter solstice and the spring equinox — astronomical Imbolc is when the sun reaches 15° Aquarius, though the traditional date is fixed at 1 February.
The earliest written evidence for Imbolc as a festival comes from the 10th-century Cath Maige Tuired and from medieval Irish glossaries. The festival is associated with the goddess Brigid — one of the most important deities of the Irish pantheon — and with the practical agricultural reality of early February: the ewes begin to come into milk at this time, providing the first fresh food of the year after the long hungry winter. The milk of the ewes was the sign that spring was alive somewhere in the land, even if it was not yet visible above ground.
Unlike Beltane and Samhain — which were celebrated with communal bonfires and public ceremony — Imbolc was primarily a domestic festival, centred on the hearth and the household. Brigid was invited into every home; offerings were left on the doorstep; her protective power was called on to bless the house, the livestock and the family for the coming year. The intimacy and interiority of Imbolc is part of its character — it is a festival of inner fire rather than public flame.
The festival's astronomical position makes its quality intelligible: at the midpoint between the darkest day (winter solstice) and the equal day (spring equinox), the days are noticeably longer than at midwinter but spring has not yet arrived. The light has turned — this is the crucial fact of Imbolc — but the world has not yet responded. Imbolc celebrates the turning that precedes the change. It is the festival of hope and potential, of the fire that burns in the depths before it breaks the surface.