Mich. Comp. Laws § 435.351

Sec. 1. (1) In recognition of the men and women who have lost their lives in the line of duty while serving as law enforcement officers in the state of Michigan, May 15 of each year shall be known as "Police Officers Memorial Day". (2) In recognition of the men and women who have lost their lives while serving as firefighters in the state of Michigan, May 4 of each year shall be known as "Firefighters Memorial Day".