Why Seventh-Day Adventists worship on Saturday

You might be wondering why we worship on Saturday instead of Sunday. The answer is simple. Let me explain…
God loves us. He loves us so much he sent his Son, Jesus, to die for us, to die a death you and I inevitably will face and unfortunately deserve (John 3:16). The Good News is if we choose to believe in Him and accept Him, and this gift of grace (Ephesians 2:8, 9), we can have eternal life.
As a response to God’s love and great gift, we want to do our best to please Him and follow his commands (John 14:15), not because they are the path to salvation, but as a response to His love for us. One of those commands is “To remember the Sabbath day and keep it holy…six days shall you labor and do all your work, but the Seventh Day is the Sabbath of the Lord your God.” (Exodus 20:8-11)
So, that is our goal…to please God by remembering the Sabbath. We understand that well meaning, God loving Christians, disagree about things, and that many Christians worship on Sunday in a desire to celebrate the resurrection of Jesus and honor the traditions established by the Church of the past. Our desire is to honor God to the best of our ability and Biblical understanding. Below are the reasons why we believe the Bible Sabbath is the Seventh Day and not the First Day, and why, although we love our First Day brothers and sisters, choose to worship on Saturday.
Reason one: The Sabbath Was Given at Creation (so it is not a Jewish holy day, but God's). The Sabbath was instituted by God's own example on the seventh day of creation week. "And on the seventh day God ended his work which He had made; and he rested on the seventh day from all his work which He had made. And God blessed the seventh day, and sanctified it; because that in it he had rested from all his work which God created and made" (Gen. 2:2-3).
Reason two: God commands us to keep it in the Ten Commandments, "Remember the Sabbath day, to keep it holy. Six days you shall labor, and do all thy work: But the seventh day is the Sabbath of the Lord your God: in it you shall not do any work. For in six days the Lord made heaven and earth, the sea, and all that in them is, and rested the seventh day: Therefore the Lord blessed the Sabbath day, and hallowed it." (Exodus 20:8-11)
In the New Testament, the Ten Commandments are consistently upheld as reflecting God's will for mankind. Jesus reinforced the Ten Commandments (Mark 10: 17-19). So did Paul and James (Rom 2:13, 21; 7:7-14, 21; Jas. 2:8-12), and all his closest followers.
As Christians, we don’t choose to ignore the other nine, why do we change or ignore the 4th Commandment? We believe the seventh day Sabbath is part of God’s law.
Reason Three: Jesus Upheld the Sabbath. During His earthly ministry, Jesus declared that the Sabbath was made for man, that is, all of mankind and not just for the Hebrews or Jews (Mark 2:27). All throughout His earthly ministry, Jesus observed the Sabbath (Luke 4:16)
Reason Four: The apostles continued to keep the Sabbath following Jesus' death. Contrary to popular belief, there is no evidence that they abandoned the seventh day of the week for the first day. Luke 23:56, Acts 17:2; 18:4, Acts 13:14-15.
Also, there is no evidence that the early church began worshiping on Sunday; in fact the term "first day of the week" is used only eight times in the New Testament, and none of these mentions anything about its being a special day in any respect. One, 1 Corinthians 16:2, even suggests that the day was to be used for work, for taking an inventory and laying aside an offering at home!
Reason Five: Sunday Adopted for Political Reasons in Post-apostolic Times. History reveals that it was because of political and social pressures that the Sabbath was gradually abandoned for Sunday-long after the time of the Apostles. Severe anti-Jewish attitudes developed in the Roman world during the first and second centuries. As acts of repression, the Romans outlawed circumcision, sacrificing, Sabbath keeping and other Jewish practices.
Consequently, Christians, particularly at Rome, found it expedient to put as much distance as possible between themselves and the Jews, to demonstrate to the Romans that they were not Jewish. One way they did this was to work on the Sabbath. Sunday, which was already used by many Romans as a holiday, was a convenient substitute
When Constantine officially recognized Christianity in the fourth century, he put the power of the empire behind Sunday observance. In the centuries that followed, the first day of the week became firmly entrenched as the "Christian Sabbath" that even Protestant reformers could not dislodge it, though they claimed their authority from the Bible and Bible only.
By the way, some calendars these days show Monday as the first day of the week and Sunday as the seventh day, so you may wonder why we consider Saturday to the be seventh day. All four followers of Jesus who wrote biographies about Him in the Bible recorded that Jesus rose from the dead early on the first day of the week (Matthew 28:1; Mark 16:2; Luke 24:1; John 20:1).
Also, in the first few centuries of the common era (A.D.), Christian leaders moved God's holy day from the seventh day of the week to the first day, or Sunday, citing Jesus' resurrection from the dead on that day as the reason for the change (see a passage from Justin Martyr, A.D. 110-165, http://www.ccel.org/ccel/schaff/ anf01.viii.ii.lxvii.html).
Even though some calendar makers have numbered the days of the week differently since the mid-20th century, we can know what God meant when He said, "the seventh day is a Sabbath of the LORD your God" (Exodus 20:10).