29 C.F.R. § 4.178

Since employees subject to the Act are entitled to the minimum compensation specified under its provisions for each hour worked in performance of a covered contract, a computation of their hours worked in each workweek when such work under the contract is performed is essential. Determinations of hours worked will be made in accordance with the principles applied under the Fair Labor Standards Act as set forth in part 785 of this title which is incorporated herein by reference. In general, the hours worked by an employee include all periods in which the employee is suffered or permitted to work whether or not required to do so, and all time during which the employee is required to be on duty or to be on the employer's premises or to be at a prescribed workplace. The hours worked which are subject to the compensation provisions of the Act are those in which the employee is engaged in performing work on contracts subject to the Act. However, unless such hours are adequately segregated, as indicated in § 4.179, compensation in accordance with the Act will be required for all hours of work in any workweek in which the employee performs any work in connection with the contract, in the absence of affirmative proof to the contrary that such work did not continue throughout the workweek.