On what date did Spirit last communicate with Earth?

Spirit last communicated with Earth on March 22, 2010.

By then, Spirit had been immobilized in soft Martian soil near a feature called Troy. NASA had spent months trying to free the rover, but in January 2010 it abandoned the effort and repurposed Spirit as a stationary science platform.

The rover's final communication came as the Martian southern winter approached. Spirit was stuck on relatively flat ground rather than a sun-facing slope, so its solar arrays could not gather enough energy to keep its batteries and survival heaters operating. NASA expected it might enter low-power hibernation, but no later communication was received.

The date marks the last contact, not the formal end of the mission. Engineers continued listening and sending commands for more than a year. NASA ended those recovery efforts and declared the mission complete on May 25, 2011. Spirit had vastly exceeded its planned 90-sol surface mission.