As the light lengthens, so the cold strengthens
Imbolc is defined as a cross-quarter day, midway between the winter solstice (Yule) and the spring equinox (Ostara). The precise astrological midpoint in the Northern hemisphere is when the sun reaches fifteen degrees of Aquarius.
The term "Imbolc" translates as either "in milk" or "in the belly," and marked the birth and nursing of the spring lambs as a sign of the first stirrings of spring in the middle of winter.
It may also have been celebrated with the lighting of candles, as slightly longer days begin to be noticeable at this time of year.
Since the Celtic year was based on both lunar and solar cycles, it is most likely that the holiday would be celebrated on the full moon nearest the midpoint between the winter solstice and vernal equinox, or when the primroses, dandelions, or other spring flowers rise up through the snow.
There's a big fuck-off clock up in the sky tonight.
It's called Candlemas in the Christian calendar and is the last feast in the Christian year that is dated by reference to Christmas - forty days after the nativity.
Under Mosaic law, a mother who had given birth to a man-child was considered unclean for seven days; moreover she was to remain for three and thirty days "in the blood of her purification." Candlemas therefore corresponds to the day on which Mary, according to Jewish law should have attended a ceremony of ritual purification.
The ceremony was usual in medieval England, where it was called 'churching'. New mothers who had yet to be churched were regarded as attractive to the fairies, and so in danger of being kidnapped by them.
The term "Candlemas" refers to the practice found in former Roman Missals whereby a priest on February 2 would bless the candles for use during the year (said candles must be of beeswax).
"Down with the rosemary, and so
Down with the bays and mistletoe ;
Down with the holly, ivy, all,
Wherewith ye dress'd the Christmas Hall"
— Robert Herrick (1591–1674), "Ceremony upon Candlemas Eve"
As the poem by Robert Herrick records, the eve of Candlemas was the day on which Christmas decorations of greenery were removed from people's homes; for traces of berries, holly and so forth will bring death among the congregation before another year is out.
Another tradition holds that anyone who hears funeral bells tolling on Candlemas will soon hear of the death of a close friend or relative; each toll of the bell represents a day that will pass before the unfortunate news is learned.
Good weather at Candlemas is taken to indicate severe winter weather later. In America Candlemas evolved into Groundhog Day celebrated on the same date.
In France, Candlemas is celebrated with crêpes, which must be eaten only after eight p.m. If the cook can flip a crêpe while holding a coin in the other hand, the family is assured of prosperity throughout the coming year.
There are those who would argue that that Candlemas is not a Christianisation of the pagan festival of Imbolc.