TES already has a holiday on December/Evening Star the 25th, which is Saturalia.
The New Life festival comes a few days early in Wayrest with Saturalia, traditionally held on the 25th of Evening Star. Originally a holiday for a long forgotten god of debauchery, it has become a time of gift giving, parties, and parading. Visitors are encouraged to participate.
Even though it does resemble some solstice celebrations, and almost shares a name with the roman festival Saturnalia, it's still a holiday for itself, and not some kind of knockoff.
Point of the story: making up new holidays for your fantasy world is usually better, and more creative than importing from Earth.