In the Star Trek universe First Contact Day is a holiday celebrated to honor the flight of the Phoenix and First Contact (as shown in the movie Star Trek : First Contact) with the Vulcans on April 5, 2063. On Earth, children get the day off from school, a fact Captain Janeway remembered was really the only way they used to celebrate it.
The Phoenix was the first human spaceship to break the speed of light and First Contact was initiated on the evening of April 5, 2063, when a Vulcan survey ship, the T’Plana-Hath, having detected the warp signature of the Phoenix, touched down in Bozeman, central Montana, where they met with the Phoenix’s designer and pilot, Zefram Cochrane. This event was generally referred to as the defining moment in Human history, eventually paving the way for a unified world government and, later, the United Federation of Planets.