In organizations where you have multiple companies or you acquire a business, employees may have a hire date that is different than a seniority date (date that the vacation accrual or RSP contribution rates are based on). For example, if you acquire a business on Jan 1, 2024 the employee's hire date with your company is Jan 1, 2024, but their seniority date for vacation accrual will be whatever start date they had with their previous company.