Flexible schedules; computation of premium pay

For purposes of determining compensation for overtime hours in the case of an employee participating in a program under section 6122 of this title— Notwithstanding section 5545(a) of this title, premium pay for nightwork will not be paid to an employee otherwise subject to such section solely because the employee elects to work credit hours, or elects a time of arrival or departure, at a time of day for which such premium pay is otherwise authorized, except that— if an employee is on a flexible schedule under which— Notwithstanding section 5343(f) of this title, and section 7453(b) of title 38, night differential will not be paid to any employee otherwise subject to either of such sections solely because such employee elects to work credit hours, or elects a time of arrival or departure, at a time of day for which night differential is otherwise authorized, except that such differential shall be paid to an employee on a flexible schedule under this subchapter—