Conn. Gen. Stat. § 53-303: Persons who observe Saturday excepted from Sunday law.

No person who conscientiously believes that the seventh day of the week ought to be observed as the Sabbath, and actually refrains from work, labor or business on that day, or who conscientiously believes that the Sabbath begins at sundown on Friday night and ends at sundown on Saturday night, and actually refrains from work, labor or business during said period, shall be liable to prosecution for performing work, labor or business on Sunday.