IAU academic calendars closely mirror the typical US academic year calendar and are updated each year. Fall and spring semesters are 15 weeks, summer terms are three or six weeks, and January-term traveling seminars are three weeks. Customized and faculty-led programs vary in length based on the structure of the program. Published calendars are considered final unless otherwise stated. Public holidays and school breaks are noted in the calendar, and students should plan to arrive on the published Arrival Date. Classes run from Monday through Friday, and attendance is mandatory.