Michigan Compiled Laws, Chapter 45. Counties § 45.318

Sec. 118. Each of the officers named in this chapter,  1 except notaries public and prosecuting attorneys, shall before entering upon the duties of his office, and within 20 days after receiving official notice of his election, or within 20 days after the commencement of the term for which he was elected, take and subscribe the oath of office prescribed by the constitution of this state, before some officer authorized by law to administer oaths, and deposit the same with the clerk of the proper county, who shall file and preserve the same in his office.