Michigan Compiled Laws, Chapter 330. Mental Health Code § 330.1479

Sec. 479. All leaves or absences from a hospital, other than release or discharge, and all revocations of leaves and absences under section 408,  1 shall be governed in accordance with rules or procedures established by the department or the hospital; except that a hospital director shall discharge any patient who has been hospitalized subject to an order of continuing hospitalization and who has been on an authorized leave or absence from the hospital for a continuous period of 1 year. Upon such discharge, the hospital director shall notify the court.