Well, for starters, Jesus wasn’t born in December. Way too cold for shepherd to be out with their sheep at night in Israel. Bases on the Scriptures, it appears that it is most likely that Jesus was born in the fall, most likely during the “feast of Tabernacles”, the Feast of Ingathering or Sukkot, celebrated in the month of Tishrei, which varies from late September to late October.
Saturnalia was typically characterized by gift-giving, feasting, singing and lots of debauchery. The priests of Saturn would carry wreaths of evergreen boughs in procession throughout the pagan Roman temples.