Which of these holidays is not a federal holiday in the United States?

Valentine's Day is not a federal holiday in the United States. Federal holidays are designated by Congress and include celebrations that are recognized nationwide, such as Independence Day, Christmas, and Thanksgiving. These holidays involve official observances and often lead to federal government offices being closed.

In contrast, Valentine's Day is celebrated on February 14th and is primarily recognized as a cultural and commercial event that honors romantic relationships. It does not carry the same official status, so federal employees do not receive time off on this day, marking it as distinct from the other options. This differentiation is important for understanding the significance of federal holidays and their impact on work and government functions in the United States.