The uniform state payroll system may provide for the fixing of staggered payroll periods, and designated days of the month on which permanent monthly salaried employees shall be paid for the preceding payroll period. These pay dates shall not be more than 10 calendar days following the close of the payroll period for monthly salaried employees and not more than 15 calendar days following the close of the payroll period for semimonthly and biweekly payroll systems. No change shall be made pursuant to this section in the existing payroll periods of a bargaining unit unless the change is authorized or approved in the memorandum of understanding for that

unit.