Employers are not required by law to provide vacation time off or vacation pay. Vacation time/pay is a fringe benefit controlled by the company and can be offered or taken away.   Under Public Act 390 of 1978, the Payment of Wages and Fringe Benefits Act, section 3 provides, "an employer shall pay fringe benefits to or on behalf of an employee in accordance with the terms set forth in the written contract or written policy."

If an employer has a written contract or vacation policy that requires you to use your paid vacation time during a scheduled shutdown time period, then the employer is required to pay you as described in the written contract or vacation policy for the scheduled shutdown time period.   If there is no written contract or vacation policy, an employer is only required by law to pay you for all time worked; if you did not work for the employer during the scheduled shutdown time period, then the employer would not be required to pay you for the scheduled shutdown time period.