a repost of sorts
https://infogalactic.com/info/Christmastide
In medieval era Christendom, Christmastide “lasted from the Nativity to the Purification.”[note: February 2][33][34] To this day, the “Christian cultures in Western Europe and Latin America extend the season to forty days, ending on the Feast of the Presentation of Jesus in the Temple and the Purification of Mary on 2 February, a feast also known as Candlemas because of the blessing of candles on this day, inspired by the Song of Simeon, which proclaims Jesus as ‘a light for revelation to the nations’.”[35] Many Churches refer to the period after the traditional Twelve Days of Christmas and up to Candlemas, as Epiphanytide, also called the Epiphany season.[8][36]
The contemporary or ancient shorter season:
Christmastide begins very early on 25 December. Historically, the ending of Christmastide was 5 January.
Similarly there is a post-Easter celebration called “Eastertide”:
Eastertide is the period of fifty days from Easter Sunday to Pentecost Sunday.[2]