It is not necessary for Christians to keep the sabbath on Saturday.
When Gentile Christians asked about keeping the ceremonial laws of Moses, it was told them the following:
"The apostles and the brethren who are elders, to the brethren in Antioch and Syria and Cilicia who are from the Gentiles, greetings.
Since we have heard that some of our number to whom we gave no instruction have disturbed you with their words, unsettling your souls,
it seemed good to us, having become of one mind, to select men to send to you with our beloved Barnabas and Paul,
men who have risked their lives for the name of our Lord Jesus Christ.
Therefore we have sent Judas and Silas, who themselves will also report the same things by word of mouth.
For it seemed good to the Holy Spirit and to us to lay upon you no greater burden than these essentials:
that you abstain from things sacrificed to idols and from blood and from things strangled and from fornication; if you keep yourselves free from such things, you will do well. Farewell." (Acts 15:23-29)
So Christians do not need to keep the laws regarding the sabbath, circumcision, clean/unclean foods, etc. Even Apostle Peter (a Jew) lived like Gentile (Galatians 2:14).
In fact, not even Jesus kept the sabbath all the time. "For this reason the Jews were persecuting Jesus, because He was doing these things on the Sabbath. But He answered them, 'My Father is working until now, and I Myself am working.' For this reason therefore the Jews were seeking all the more to kill Him, because He not only was breaking the Sabbath, but also was calling God His own Father, making Himself equal with God." (John 5:16-18)
Scripture says that Jesus broke the sabbath by working. Not only this, but God the Father has been working everyday and Jesus also.
The sabbath was instituted to give people rest at least one day of the week. Otherwise, people in ancient times would work everyday and be exhausted.
However, now that we have Jesus, who is our rest, we can rest in God everyday. "Jesus said to them, 'The Sabbath was made for man, and not man for the Sabbath. So the Son of Man is Lord even of the Sabbath.'” (Mark 2:27-28)
Jesus said, “Come to Me, all who are weary and heavy-laden, and I will give you rest.” (Matthew 11:28)
Therefore, there is no better rest than Jesus. When we have Him, we are free from the law. So we can choose to work even on the sabbath.
"Therefore no one is to act as your judge in regard to food or drink or in respect to a festival or a new moon or a Sabbath day— things which are a mere shadow of what is to come; but the substance belongs to Christ." (Colossians 2:16-17)
Many Seventh Day Adventists are enslaved by law and legalism. The apostle Paul worried about such Christians. He feared that they wanted to live by law and be saved by law, instead of being saved by Jesus.
"But now that you have come to know God, or rather to be known by God, how is it that you turn back again to the weak and worthless elemental things, to which you desire to be enslaved all over again? You observe days and months and seasons and years. I fear for you, that perhaps I have labored over you in vain." (Galatians 4:9-11)
Therefore, we should not judge one other regarding these non-essential things. Each person is free to worship or observe any day he wishes.
"One person regards one day above another, another regards every day alike. Each person must be fully convinced in his own mind. He who observes the day, observes it for the Lord, and he who eats, does so for the Lord, for he gives thanks to God; and he who eats not, for the Lord he does not eat, and gives thanks to God. For not one of us lives for himself, and not one dies for himself; for if we live, we live for the Lord, or if we die, we die for the Lord; therefore whether we live or die, we are the Lord’s. For to this end Christ died and lived again, that He might be Lord both of the dead and of the living.
But you, why do you judge your brother?" (Romans 14:5-10)
So it’s fine if a person wants to observe the sabbath. It’s also ok if a person doesn’t observe the sabbath. The church is not under the Old Testament legal system. "For the law was given through Moses, but grace and truth came by Jesus Christ" (John 1:17).
Seventh Day Adventism has unbiblical doctrines and legalism. As Christians, we should focus on loving God and loving people (Matthew 22:36-40), instead of on what day to observe. To learn more, please see:
https://www.gotquestions.org/Seventh-Day-Adventism.html