Mich. Comp. Laws § 168.596

Sec. 596. The state convention held for the purpose of nominating candidates for state offices to be voted for at the November election shall be known as the "fall" state convention and the county convention held for the purpose of electing delegates to the fall state convention shall be known as the "fall" county convention. The state convention held not less than 37 days before the first Monday of April in every odd numbered year shall be known as the "spring" state convention, and the county convention held for the purpose of electing delegates to the spring state convention shall be known as the "spring" county convention.