Starting and closing dates for each semester, scheduled holidays, and other important scheduling information can be found in the academic calendar. Undergraduate class periods are sometimes 80 minutes in length, meeting twice a week, and sometimes 160 minutes in length, meeting once a week. Graduate class periods are typically 160 minutes in length, meeting once a week unless otherwise specified. There are 15 weeks of instructional activity for each course. The Thanksgiving week schedule is rearranged to allow all classes to meet 15 sessions during the semester. The majority of graduate classes are offered starting at 4:30 p.m. or 7:20 p.m. Most courses in the Ph.D. in industrial relations and human resources program are offered between 9 a.m. and 5 p.m.