Which of the following is NOT a federal holiday?

Valentine's Day is not a federal holiday, which is why it is the correct answer. Federal holidays are designated by the United States government and are recognized nationwide, during which federal employees typically have the day off and federal offices close. Independence Day, Columbus Day, and Memorial Day are all recognized federal holidays, each celebrating significant events or figures in American history. Valentine's Day, on the other hand, is widely celebrated culturally, but it does not hold the status of a federal holiday and thus does not come with any official government observance or implications such as time off work for federal employees.