Every wage and hour calculation under the Fair Labor Standards Act runs on one fixed unit: the workweek. § 778.105 defines it precisely — a fixed and regularly recurring period of 168 hours, seven consecutive 24-hour periods. It doesn’t have to match the calendar week; it can start on any day and at any hour an employer chooses, and different workweeks may be set for different employees or groups. But once that starting point is set, it stays fixed no matter what schedule the employee actually works. An employer can change it later, but only if the change is meant to be permanent — not a one-off shift used to dodge overtime.

Each workweek stands alone. § 778.104 is explicit that the Act does not permit averaging hours over two or more weeks — an employee who works 30 hours one week and 50 hours the next is owed overtime for the hours over the applicable maximum (40 hours in a workweek, per § 778.101) in that second week, even though the two-week average comes out to 40. That rule holds regardless of how the employee is actually paid: daily, weekly, biweekly, monthly, by the piece, or on commission. A biweekly or monthly pay cycle doesn’t create a biweekly or monthly overtime calculation; hours worked and pay owed still have to be figured out workweek by workweek.

The workweek is also the unit the employer totals hours against. § 778.103 requires adding up all the hours an employee worked in that single workweek, even across two or more unrelated assignments, and — where an employee works for more than one employer, a situation known as joint employment — combining the hours worked for all of them. The same fixed period does double duty as the standard for deciding whether the Act applies at all: under § 776.4(a), if an employee does any covered work (work that is “engaged in commerce or in the production of goods for commerce” under §§ 776.8 and 776.15, or that qualifies for enterprise coverage under § 776.22a) in a given workweek, the entire week’s work is treated as covered — unless the employee is exempt (that is, specifically excluded from these requirements by another provision of the Act) — regardless of how small a share of the week that covered work was.