I hope I remembered the primary December observances and celebrations.
Did I miss any?
Hanukkah - The Jewish Festival of Lights
beginning the evening of Tuesday, December 12, ending the evening of Wednesday, December 20.
St. Lucia Day Festival of Lights
Wednesday, December 13
Winter Solstice Thu Dec 21 16:28 GMT
Christian (Brethren, Catholic, Mormon, Presbyterian, etc.)
Dec 25th to the Feast of the Epiphany on Jan 6th
LightTheWorld - LDS Christmas Celebration for 2017
Kwanzaa 2017 in United States of America will begin on Tuesday, December 26
and ends on Monday, January 1, 2018
Three Kings Day
Friday, January 6 Epiphany 2017
Merry Christmas, Happy Holidays, and Happy New Year!