NASA's decision to launch Surveyor on 7 November 1996 was not an arbitrary choice, nor was it based on when management thought the spacecraft would be ready for flight. Instead, the November choice depended on the exact positions of the Earth and Mars relative to the Sun.
The reason for this geometrical dependence is that in spaceflight, straight-line paths do not exist. All planets move in long, curved paths around the Sun that take the shape of circular and elliptical orbits. In order to reach Mars, Surveyor must first depart Earth and then coast in an elliptical orbit around the Sun that will eventually intersect the orbit of Mars.
The tricky part involved timing the launch to allow Surveyor and Mars to arrive at the same point in space at the same time. Engineers on the flight team refer to the dates when Mars and Earth are aligned in the right position for launch as the "launch window" or "launch period." Surveyor's launch period opened on 6 November 1996 and closed on 25 November 1996.