Dead right Yorick, datal seniority is a concept whose time has come and gone.
The only criteria for promotion should be and must be merit. Time in the company would be only one component of 'merit' , which should also include qualifications, experience and job performance.
The industry has change over the last 20 years and outmoded promotional systems such as datal seniority simply have no place in contemporary flight operations. Datal seniority is a concept that simply is not supported by ANY respected resource managment philosophy.