Assistant Instructors. Regular full-time Assistant Instructors shall be entitled to 30 work days of vacation per calendar year, earned on the basis of 2.5 work days per calendar month for each calendar month an employee has received at least ten (10) days pay. After five (5) years of employment, a regular full-time Assistant Instructor shall receive one (1) additional day of vacation (equal to 0.083 days per calendar month) for each additional year of employment up to a maximum of ten (10) additional days. Upon reaching twenty (20) years service, an Assistant Instructor shall be entitled to an additional 4 days of vacation per year (equal to 0.333 days per calendar month).