Mich. Comp. Laws § 435.131

Sec. 1. Whenever in the statutes of this state, rights, privileges, immunities or exemptions are given or duties and responsibilities are imposed on persons who conscientiously believe the seventh day of the week ought to be observed as the sabbath, said sabbath or seventh day shall mean and be construed in accordance with the worship and belief of such persons to include the period from sunset on Friday evening to sunset on Saturday evening.