Work hours of supervisors vary greatly among establishments, because work schedules usually depend on customers' needs. Supervisors generally work at least 40 hours a week. Long, irregular hours are common, particularly during sales, holidays, busy shopping hours, and times when inventory is taken. Supervisors are expected to work evenings and weekends, but usually are compensated with a day off during the week. Hours can change weekly, and managers sometimes must report to work on short notice, especially when employees are absent. Independent owners can often set their own schedules, but hours must be convenient to customers.