These dates in the Christian calendar are long standing traditional pre-Christian festivals. These are traditions of the British Isles stretching back thousands of years, they are an important part of the history of these islands we live on. As a Brit, Christianity doesn’t resonate with me at all, it just all seems like some localised Middle Eastern cult stories about some Aramaic speaking bloke from Judaea and the god they worshipped. It only took a foothold here because of Constantine I and the size and success of the Roman Empire. If Rome had collapsed centuries earlier, I doubt Christianity would ever have been more than just another cult religion of the Middle East and Mediterranean at a specific moment in time like so many other cult religions in the region in the centuries around then. The cult of Christ at that time wasn’t anything to do with Britain, the Middle East was miles away, in another part and culture of the world; at least these pagan festivals and gods/goddesses have their history here in the British Isles.
Not that the Celtic and Germanic gods and goddesses of Northern Europe resonate with me either, but I see past them and relate all these festivals to their relation to astronomy and the seasons. Which is what they are really about. To me wanting to keep the tradition of Easter isn’t about celebrating the goddess Ēostre and her fertility, it’s about the Proto-Indo-European root of the word Hausos going back to ~4,500 years BCE and what it means and relates to - where the Sun rises at dawn in the East at the Vernal Equinox, and the coming of Summer.
The Coligny and Villards d'Herias calendar tablets show the Celtic months over five years and what festivals were celebrated in them. With Germanic runic calendars having dates for festivals at exactly the same time, with similar celebrations but with different names. Pliny the Elder wrote about the Celtic and Germanic festivals in his book Natural History from the 1st century CE. They’re all there in the pre-Christian record.
There’s no way that, after Christianity set its dates for its festival calendar, it was a pure coincidence that they ran almost identically to the pre-Christian festivals which also just happened to be at the astronomical and phenological major points of the year. The Christian church appropriated these festivals, and adapted them to suit the Christian church and even moved some to the pagan dates to make it easier to get the pagans to convert to Christianity - the Puritans banned Christmas in Britain because they said it was a pagan festival and that the of the birth of Jesus wasn’t around the Winter Solstice, it was moved there to coincide with the major Northern European festival that that time of year.
It’s why pre-Christian symbolism lives on through a lot of them despite the festivals being taken over by Christianity - evergreens at Christmas and Cupid at Valentine’s, for example. It’s also why the etymology of the festival names derive from very ancient Northern European languages (far pre-dating Christianity’s move Northwards) which relate to phenology - Lent and Easter, for example. And why the names and stories of many Saints are actually taken from pre-Christian gods/goddesses that were celebrated on these festivals - take Brigid/St Brigid and Mars/St Martin, for example.
