Inauguration Day is a "partial" Federal holiday.
Unlike others, which are observed annually across the entire Federal workforce everywhere, Inauguration Day is only celebrated 1) when a President is inaugurated (on January 20 only in the years following a Presidential election) and 2) then only in the Washington, DC metropolitan area (which is specifically defined as the District of Columbia, the counties of Montgomery and Prince George's in Maryland, the counties of Arlington and Fairfax and the independent cities of Alexandria, Fairfax, and Falls Church in Virginia), primarily to avoid severe traffic jams due to people attending the inauguration ceremonies. Outside of the DC metro area and in other years, it is not a paid holiday.