To get everyone on the same page lets start with some general information about Imbolc:
Imbolc is celebrated from February 1st to the 2nd and yes, it is considered a pagan holiday *gasp*. This holiday marks the halfway point between winter solstice and spring equinox, because of this it celebrates both seasons and the change of the seasons. Since this holiday is pre-christian and nature based it is typically celebrated by Wiccans, neopagan, and pagan influenced religions, but it is not limited to those groups.
Imbolc can be traced back to the 10th Century, where it is mentioned in an Irish poem and the poem associates purification with the holiday. Sheep are a big deal in Ireland and around this time of year is when they start lactating. Which is why Imbolc is also speculated to be linked to rebirth, well a sheep's and the earth's rebirth at least. This holiday is Celtic and has a Celtic goddess (a woman in power :0) associated with it.
Who is this Celtic goddess?
Her name is... Brigid and she represents fertility, poetry, crafts, and prophecy. Brigid is also known as one of the most powerful goddesses in the Celtic religion. She is the daughter of Dagda (aka) the oldest god in the Celtic religion. Speaking of family, Brigid is thought to have two sisters with the same name as her, although many people believe that they are all actually one goddess and each "sister" represents a different side of this magnificent goddess. A little fun fact about Brigid: when she was born it has been rumored that she was born with a flame on her head and drank milk from a magical cow in the spiritual realm.
Ancient celebrations of Imbolc!
This is my favorite category, I don't know about the rest of you, but I am a history fanatic. Like I said earlier this holiday dates all the way back to the 10th century, sadly I couldn't find a lot of history specifically about this holiday and how it was celebrated. I did find that they used to make effigies of Brigid out of bundles of oats and rushes. Once they finished their effigies they would clothe them in dresses and leave them in a basket overnight. The day of Imbolc they would celebrate by lighting campfires, lanterns, and lamps.
The modern celebration of Imbolc!
Imbolc is more of a low key celebration in modern times; typically more of a personal reconnection with nature. The holiday is also more fluid, it doesn't exactly have a set date, the day it is celebrated all depends on where you live and when the seasons start to change. Modern effigies are also made out of corn rather than bundles of oats and rushes, although some tend to stick to the traditional celebrations.