Simplify the following text for a Grade 17 native English-speaking person.
Original: Seventh-day sabbatarians point to the fact that the seventh day Sabbath was kept by the majority of Christian groups until the 2nd and 3rd century , by most until the 4th and 5th century , and a few thereafter , but because of opposition to Judaism after the Jewish-Roman wars , the original custom was gradually replaced by Sunday as the day of worship .
Simplified: Seventh-day Sabbatarians claim that the seventh day Sabbath was kept by the majority of Christian groups until the 2nd and 3rd century , by most until the 4th and 5th century , and a few thereafter , but because of opposition to Judaism after the Jewish-Roman wars , the original custom was gradually replaced by Sunday as the day of worship .