Legel Holidays can be established by Federal and State Governments. Establishment of a legal holiday generally means that Federal and/or State Offices are closed and Federal and/or State Employees receive a day off from work. If the holiday falls on a weekend, the Employees generally receive a day of prior or after the weekend holiday date.
The US Office of Personnel Management states:
Federal law (5 U.S.C. 6103) establishes the following public holidays for Federal employees. Please note that most Federal employees work on a Monday through Friday schedule. For these employees, when a holiday falls on a nonworkday — Saturday or Sunday — the holiday usually is observed on Monday (if the holiday falls on Sunday) or Friday (if the holiday falls on Saturday).