The Sa'ami (Laplanders) called it "Day of the Dead".
It's close to December 24, and somtimes is that day. For a variety of reasons having to do with Earth's orbit, it's inclination, etc. it is not also the "shortest day of the year", which occurs about December 21.
You find echoes of this ancient celebration in the use of Christmas Eve for primary gift-giving and feasting among the Scandinavians, and various Germanic tribes here and there.
Inasmuch as the Sa'ami are essentially the same people as the ancient Sumerians who gave us written language, and whose most fundamental stories seem to have served as the basis for much of the Bible, it seems quite appropriate to see their time of celebration maintained in Christian practice.
Undoubtedly this happened as a consequence of the inspiration of the Holy Spirit and has absolutely nothing to do with the Roman worship of Saturn, also known as Ba'al, over whose fires so many tens of thousands of infants were sacrificed throughout the Middle East in ancient times.
Did not know that. Interesting.