Seniority date - Legal Entity Hire Date or Rehire date

Summary:

Requirement to identify the Lenth of Service based on Rehire date

Content (please ensure you mask any confidential information):

We have requirement to accrue the leave balance based on below,

New Hire – Legal Entity Seniority date can be used to determine the Length of service in the organization.

Global Transfer cases – Legal Entity Seniority date can be used to determine the Length of service in the organization.

Rehire cases – Seniority date can’t be used and should use rehire date to determine the length of service.

Could anyone share how we can write a fast formula of type 'Length of Serivce date to Use' to handle the above scenarios.