State service for the purpose of determining which vacation accumulation rate in the schedule in subsection (a) of Section 42904 to use shall include all qualifying monthly pay periods of service. Part-time qualifying service at the rate of one-half time or more shall be counted as full-time service. Part-time qualifying service at a rate of less than one-half time shall be accumulated until it is equal to one month of full-time service (e.g., 4 months of one-fourth time service equal one qualifying monthly pay period) at which time it shall be credited to the employee.

For purposes of the schedule in subsection (a) of Section 42904, 160 hours of service of an hourly employee equals one qualifying monthly pay period. However, hours worked in a monthly pay period in excess of 160 shall be carried forward to the next accumulation. Not more than 160 hours may be credited in any one pay period.

When a person employed half-time or more changes time base to less than one-half time or is changed to an hourly rate employee, or when a person employed less than half-time or on an hourly basis changes time base to half time or more, he or she shall retain qualifying service credit already received and shall continue accumulating qualifying service credit applicable to the new time base. Any time worked by a person employed less than half-time or on an hourly basis which does not equal a month of full-time service, upon a change in time base or return to service following a break in service, shall not be credited to the employee.

When any employee changes from less than one-half time to hourly (or vice versa), the service under each time base shall be accumulated until it equals one month of full-time service.