If employees are required to be on duty 24 hours or more, the employer and the employees can agree on bona fide meal periods and bona fide, regularly scheduled sleeping periods of at least 8 hours, as long as the employer provides adequate sleeping facilities, and the employee can usually enjoy an uninterrupted night's sleep. When an employer and employees enter into such agreements, and these conditions are satisfied, the meal and sleeping periods are not counted as hours worked. In the absence of such an agreement, meal periods and 8 hours of sleeping time are counted as hours worked. If the sleeping period is not counted as hours worked, and it is interrupted by a call to duty, the interruption counts as hours worked. The entire period of interruption must be counted if the employee cannot get a reasonable night's sleep.