The 8th day is an important day, as it signifies the Lord's reign on Earth, but would have nothing to do with Jan 1.
To understand the Bible's information that God so graciously gave us, you must study and understand Jewish history and traditions. To become Christian doesn't make you a different religion, it makes you a completed, or perfected" Jew. The Jew's for Jesus are such Jews. IMHO, the disconnect between Christians and Jews is where the antisemitism sprouts. Why would we, or should we, keep denying that Jesus was a Jew, lived as a Jew, and gave His life on Passover, was placed in the grave on Unleavened Bread, and rose on First Fruits? The Holy Spirit was given on Passover and I believe, we will be Raptured on a future Feast of Trumpets, Judgement day will be some future Yom Kippur, and the 1000 years reign of Christ will follow on a future Tabernacles. The words "dwelt with us" as used in John:1, come from a translation of "tabernacled with us" and that is the only use of that particular phrase in the Bible. The writer of John was telling us that in the beginning was the Word, , and the Word was God, and the Word came and dwelt,or tabernacled, among us.
There is a complicated search you can do starting in Luke to follow the "course of Abijah" which will lead you to the birth of John the Baptist,and then to the birth of Jesus on Tabernacles. A study of the Jewish Feast Days are easily found and will open the Bible and it's prophesy to Christians and give new meaning to what God has revealed about The Savior of the World.