Seniority Dates are the dates the company uses for layoff purposes. The Carpenters have four Occupational Titles at the present time.  Divers, Joiners and Upholsters are PREMIUM OCCUPATIONAL titles which means they can regress back into the Carpenter Title if a layoff occurs. This is very important to understand so it theory a person who gets hired into the premium occupational title and has like 5 years seniority with the company, will not be laid off if there is a layoff in the Carpenter Title.  If a layoff occurs in a premium title then that person can regress into the title from which he came from last. If a person in a premium title gets laid off and did not have any seniority at all in the Carpenter Title then he will face a layoff unless they can secure another position within the company.