The exact day has not been set, but according to the Xichang Launch Center it will happen between July 20th to 25th. This will be China’s first attempt at landing a rover on Mars. If successful, they’ll be in an exclusive group with NASA/USA. In a dramatic coincidence, NASA is also planning to launch their Perseverance Rover to Mars in the same launch window.
If the launch goes according to schedule, the Tianwen-1 lander and rover will reach the surface of Mars in February 2021. The rover’s mission is scheduled to last about 90 days, and the launch vehicle is a Long March 5 rocket.