Source: http://askthelawyer.federaltimes.com/2011/01/10/q-a-session-compensatory-time-off/
Timestamp: 2019-04-19 23:14:00+00:00

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Is an employee entitled to compensatory time for hours worked above the normal tour of duty of eight hours after arriving at a TDY site?
An employee on a TDY is only entitled to compensatory time off “for time in a travel status away from the employee’s official duty station when the travel time is not otherwise compensable.” 5 C.F.R. § 55.1401 (emphasis added); see 5 C.F.R. § 550.1403 (“Compensable refers to periods of time that are credible as hours of work for the purpose of determining a specific pay entitlement, even when that work time may not actually generate additional compensation because of applicable pay limitations”). Thus, if you are working more hours than regular tour of duty, as your question suggests, you will be entitled to compensatory time off for your travel to/from your work station. Additionally, you will also be entitled to compensatory time off for any time beyond your normal 8-hour tour of duty spent working at the temporary duty station. See 5 U.S.C. § 5542 and 5 C.F.R. § 550.113 (FLSA-exempt employees); 29 U.S.C. § 207(e)(7) and 5 C.F.R. § 551.531 (FLSA-nonexempt employees).

References: § 55
 § 550
 § 5542
 § 550
 § 207
 § 551