Final answer:
The Seventh-day Adventist Church observes Saturday as the holy day. They root their beliefs in the Biblical narrative of creation and the Ten Commandments.
Step-by-step explanation:
The Christian sect that maintains Saturday as the holy day is known as the Seventh-day Adventist Church. This denomination arises from the millennialist movement in the mid-19th century and is rooted in the belief of the imminent Second Coming, or 'Advent,' of Jesus Christ. Seventh-day Adventists observe Saturday, or the 'Sabbath,' as the proper day of worship based on the Biblical creation narrative in which God rested on the seventh day, and the Ten Commandments, which include keeping the Sabbath day holy.