OPM added that federal employees are being excused from duty during a pay period in which there are already two paid holidays (Christmas. Opm In Lieu Of Holiday Holidays Work Schedules And. Payroll Hours of Duty amp Leave United States Department. U S Office of Personnel Management. Federal law (5 U.S.C. ) establishes the public holidays listed in these pages for Federal employees, Friday, July 3, will be treated as a holiday for pay and.