Union Bargaining Unit Service Date for Leave Accrual

Hello!

Does anyone have experience or information on the following:

Setting up a union bargaining unit that has contracted use of a date other than the standard service date for leave accruals used by the rest of the organization.

Background:

A union bargaining unit within the organization has contracted use of a date other than the standard service date which is used by the rest of the organization for the amount of leave accrual earned monthly based on tenure.

The majority of the org is using the standard service date to calculate the Service Months defined on the Leave Plan Table which determines the amount of leave earned each month.