On what date did NASA declare Opportunity's mission complete?

NASA declared Opportunity’s mission complete on February 13, 2019. The announcement followed months of unsuccessful attempts to revive the rover after it stopped communicating during a planet-wide Martian dust storm.

Opportunity had landed on Meridiani Planum on January 25, 2004, with a design life of only 90 sols. It ultimately operated for more than 14 years on Mars, surviving dust events, mechanical problems, and the gradual aging of its systems. Its final communication had been received on June 10, 2018.

The mission was not declared complete immediately after that last transmission. NASA waited through the storm and conducted an extensive recovery campaign, sending more than 1,000 commands and listening for a response. When those efforts failed, officials formally ended the mission on February 13, 2019. The date is sometimes confused with the rover’s final signal or with Spirit’s 2011 mission conclusion.