During the early church, the majority of converts to the Way of Christ were Jews. Gentiles started to follow the truth with the teachings of Paul and others. Many of the Jewish converts still held on to the Laws of Moses and felt that it was necessary for those Laws to be followed in order to be with God.
This being the mind set, many insisted that the Gentile converts had to be circumcised and that they were required to follow the laws of the “Sabbath days, feast days” and the law of clean and unclean meats. Otherwise, the Gentiles were being told that they would be judged for committing “sins” against God and the Law of Moses.
This situation is seen in Acts 15: 5…and rose up certain from those of the sect of the Pharisees who believed (Jewish Christians), saying “It is necessary to circumcise them (the Gentile Christians) and to charge them to keep the Law of Moses (i.e. Sabbath days, feasts, times & the unclean foods, etc.).
However, Paul testified to the truth that he received from Christ and the workings of the Holy Spirit among the Gentiles, to which Peter (and the apostles) made a clear, unanimous decision and statement, saying the following…Acts 15:24-29…Inasmuch as you have heard that certain(Jewish Christians) from amongst us having gone out and troubled you by their words, upsetting your souls, saying to you that you were required to be circumcised and to keep the Law (of Moses), to whom we gave no such command, it seemed good to us with one accord…and with the Holy Spirit to no further to lay upon you this burden than (except) these necessary things: to abstain from things sacrificed to idols and from blood and from what is strangled and from fornication.
Romans 14:5 focuses on the Christian Jews’ preoccupation with the “days” in Moses’s Law……one judges a day above a day, another judges every / another day to be equal. Each in his own mind let be fully assured. He that regards the day, to the Lord regards it, and he that regards not the day, to the Lord regards not. (it is not important, and there is no sin, in what “day” the True God is worshipped as long it is the One and Only True God…through Christ His Son.
The Sabbath day is just as good as any other day to worship the True and Only God and His Son the Christ...and none should be judged as a sinner for the day of preference.
It is also understood, however, that no idol (i.e. pagan god/man’s belief) is to be worshipped on any day as Peter makes it clear by giving the instruction not to spiritually fornicate with/worship/sacrifice to any idol/ man's belief…he stresses the service to Christ and to love the One only Creator God.)
It is also seen in Galatians 4 that some of the Jewish and Gentile Christians did not easily give up their self-righteous traditions and "days" observances , causing some Christians to go back into the "physical" bondage, disregarding the love of Christ as the Only True Way of life.
...Galatians 4:8-10 …but then indeed not knowing God, you were in bondage to those who not by nature are gods, but now, having known God, but rather having been known by God, how do you turn again to the weak and beggarly elements (the days you observe, and months, and times, and years) to which again anew to be in bondage you desire?
I know that many “Christians” have justified their celebration of Christmas and Easter by claiming that they are “days” for Christ, but it is historically and factually clear that these “days” are of pagan /idol origin and substance to which the name of Christ has been added in order to “Christianize” them.
They make Christ into a religion amongst religions, perverting the truth.