If I require evening work in my unit for an event or other function, can I reduce a non-exempt staff member’s daytime hours and replace them with evening work as long as they don’t work more than 40 hours per week?

Yes, you can adjust the work hours of an employee to meet the needs of the department. When possible advance notice (a minimum of two weeks), of such changes should be given to the employee. You can rearrange hours from day to day within the same week, but the regulations do not allow you to move hours from one week to the next without incurring overtime for the week in which the hours worked exceed 40 (even if the hours worked in the preceding or following week were less than 40).  The determination of 40 hours “worked” must also include vacation and sick time, per policy.