The FLSA does not mandate specific holidays that employers must observe, and it does not require the payment of additional wages for working on holidays, unless such work results in the employee working more than 40 hours in a workweek.
When a holiday falls on a nonworkday outside a full-time employee's basic workweek, he or she is entitled to an "in lieu of" holiday. The general rule is that the "in lieu of" holiday is the workday immediately preceding the nonworkday on which the holiday fell.