Seniority

the state of being senior; priority of birth; superior age.

priority, precedence, or status obtained as the result of a person's length of service, as in a profession, trade, company, or union

First choice of vacation time will be given to employees with seniority.

noun

advantage , antiquity , eldership , precedence , preference , priority , rank , ranking , standing , station , superiority , quality , status , tenure