5 U.S.C. § 6122: Flexible schedules; agencies authorized to use

designated hours and days during which an employee on such a schedule must be present for work; and designated hours during which an employee on such a schedule may elect the time of such employee’s arrival at and departure from work, solely for such purpose or, if and to the extent permitted, for the purpose of accumulating credit hours to reduce the length of the workweek or another workday. restrict the employees’ choice of arrival and departure time, restrict the use of credit hours, or exclude from such program any employee or group of employees.