(a) Agencies begin paying an employee a COLA or post differential on the effective date of the change in the employee's official worksite to an official worksite within the COLA or post differential area or, in the case of local recruitment, on the effective date of the appointment.

(b) For an employee detailed to temporary duty in a post differential area and who is otherwise eligible for a post differential, agencies must begin paying a post differential after 42 consecutive calendar days of temporary duty in the post differential area.