Where the list of federal holidays comes from
Federal holidays are set by law in 5 U.S.C. 6103, not by custom. The statute names eleven days: New Year's Day, the Birthday of Martin Luther King, Jr., Washington's Birthday, Memorial Day, Juneteenth National Independence Day, Independence Day, Labor Day, Columbus Day, Veterans Day, Thanksgiving Day and Christmas Day. Five have fixed dates and six are defined by a weekday rule, which is why their dates change every year.
- Fixed dates: January 1, June 19, July 4, November 11 and December 25.
- Monday holidays: the third Monday in January (MLK Day) and February (Washington's Birthday), the last Monday in May, the first Monday in September and the second Monday in October.
- Thanksgiving: the fourth Thursday in November, so it falls between November 22 and 28.
The list has changed over time. The Uniform Monday Holiday Act moved several holidays to Mondays starting in 1971, MLK Day was first observed in 1986, Veterans Day returned to November 11 in 1978 after seven years on the fourth Monday of October, and Juneteenth was added in 2021. The calendar applies each rule only for the years it was in force.