|A visual comparison of the original version of the evergreen "Osiris Christ mass" tree (left), carved in stone, shown the "angel", or soul (ba) of Osiris, above the evergreen tree (Persia tree), specifically relief #18, on the walls at the Temple of Dendera, commissioned under the rule of Roman emperor Tiberius, in 14 to 37AD, and the modern Christian-version of the Christmas tree, put up during the Christmas holiday season, a festival originally called the Koiak festival spanning a 30-day period of Dec 10 to Jan 8, at the end of which the djed pillar, a metaphorical Osiris backbone (or tamarisk evergreen tree) would be raised.|
The modern Christmas season, centered around the putting up of a Christmas tree, originated, in 3,100BC, in what the Egyptians called the Khoiak festival, a celebration of the resurrection of Osiris, and the rebirth of the sun or sun god, centered around the rising of the djed pillar, symbolic of the "tamarisk evergreen tree" (or Persia tree), which, according to the "Legend of Osiris", grew up around his entombed body, was cut down, and brought into the palace of a king, as was famously summarized by Plutarch in 100AD. 
The following is the "Hermopolis version", one of about 16 varieties, of Horus (god the son, aka baby Jesus) raising Osiris (aka god the father), next to the Persia tree (Erica tree), aka Christmas tree, with the Ba or soul of Osiris, aka Christmas tree angel resting (hovering) above the tree, as depicted during the Koiak festival, on one of the walls of the Dendera Temple: 
The following are related quotes:
“1642 [Newton ’s birth] is the Christmas of the modern age.”— Johann Goethe (c.1810)
“When Darwin’s book hit the crowd, it was like Christmas for ex-Christians.”— Jennifer Hecht (2003), Doubt: a History (pg. 405)
“There is an assumption that atheists don’t ‘do Christmas’.”— Elisabeth Cromwell (2011), “A Very Atheist Christmas” 
● Christmas Tree
1. Flynn, Tom. (1993). The Trouble with Christmas (Osiris, pgs. 55-57). Prometheus Books.
2. Cromwell, Elisabeth. (2011). “A Very Atheist Christmas” (Ѻ), Washington Post, Dec.
3. Budge, Wallis. (1911). Osiris and the Egyptian Resurrection, Volume Two (pg. 40). P.L. Warner.
● Christmas – Wikipedia.
● Tom Flynn (author) – Wikipedia.