Skidmore and six others (plaintiffs) were employed as firefighters at a packing plant run by Swift & Co. (Swift) (defendant). The plaintiffs worked daytime shifts, five days per week. As part of their employment, the plaintiffs were also required to stay overnight in the fire hall on the plant’s premises three and one-half to four nights per week. The plaintiffs’ overnight duties were to respond to fire alarms. The plaintiffs were paid for any time they spent responding to alarms during their overnight stays, but they were not paid for any of their other overnight time. The plaintiffs sued Swift under the Fair Labor Standards Act (the Act), 29 U.S.C.A. § 201, seeking overtime compensation for the hours they spent overnight at the plant. The trial court referred to an interpretive bulletin issued by the administrator of the U.S. Department of Labor's Wage and Hour Division, which included standards and guidance regarding how to interpret the Act in various circumstances. The administrator's guidance suggested applying the Act flexibly, based on the degree to which an employee could conduct personal activities during on-call time and the number of consecutive hours the employee was on call without being required to actively work. Nevertheless, the trial court concluded that as a matter of law, the time the plaintiffs spent overnight on call in Swift’s fire hall did not count as hours worked for purposes of overtime compensation. The court of appeals affirmed, and the United States Supreme Court granted certiorari.