Wrong, that's not what seniority is, as was explained in the previous post to me.

For example, in FAA Air Traffic Control, our union deducted seniority time for holding management jobs, or time spent outside the ATC core job.

Even date of hire doesn't mean much. The first day that you could become a bargaining unit member was AFTER you passed your "ground school" training in Oklahoma City, therefore seniority could begin then. You were hired many months previous.