The day, Sunday, is not the Sabbath. The article is mixing up the Sabbath with Sunday...
From my understanding.....you are correct. The “Sabbat” or Sabbath is on Saturday.
Saturday is indeed the Biblical Sabbath but not the traditional sabbath for Christians.
Early Christians observed Saturday as the day of rest and the first day of the week as “The Lord’s Day” when they gathered and worshipped. They observed both because the early Christians were predominantly Jewish by birth and still upheld Jewish practices. The first day of the week was the Lord’s Day because Jesus arose on Sunday, first appeared again to the disciples who had gathered on Sunday, and was the day of Pentecost when the Holy Spirit descended upon the church in power (Acts 2).
The early church continued to observe Saturday as a day of rest and Sunday as a day of worship for the first few centuries of church history. On March 7, 321, the emperor Constantine issued a decree that made Sunday the day of rest in the Eastern Roman Empire. In Cannon 29, the Roman church in the Council of Laodicea (about A.D. 364) stated that although Christians should respect Saturday, the Lord’s Day (Sunday) should be especially honored and that no work should be done on the day of Christian worship. Pope Gregory (AD 590-604) demanded that all secular activities should cease on Sunday so that the people could devote their time to prayer. The overwhelming majority of Christian churches have observed Sunday as the day of rest and worship since then, both Catholic and Protestant.
Students of the Bible know that God judges the heart. If Christians obey His command to observe a day of rest in faith and obedience, especially honoring the Son who rose to give them new life on that day, I think God will be pleased. Likewise, I think He will be pleased with those who do so in faith and obedience on Saturday. It is the act of faith and the attitude (the heart) that matters. Observing NEITHER reveals one’s faith and attitude (heart) toward God as well. Nonbelievers should not be forced to observe those things that apply only to believers. Believers should not need a secular law to force them to obey God.