What day did the Mars landing happen?

Mars 2 was the first of many landers to reach the surface of Mars. Mars 2 was a Soviet probe launched on a Proton K rocket. The orbiter was a success, but the lander crashed on a Saturday, November 27, 1971.

The Soviet Mars 6 transmitted data during its descent, but was not heard from since before landing. It too may have crashed.

Viking 1 landed on Mars five years after the first Soviet attempt, on Tuesday, July 20th, 1976.