When is an asteroid predicted to hit earth?
At the present time, no major asteroid is predicted to hit Earth.
Asteroids with a diameter of about 5 -> 10 m hit the Earths atmosphere about once every year but are vaporised by the atmosphere with the power of a Hiroshima nuclear bomb.
Calculating the path of an asteroid is a very tricky procedure and many have been "predicted" to hit - 2002 NT7 (Not too sure is NT7 is Windows 7!) was "predicted" to hit Earth in 2019 but after analysing it's trajectory with greater detail it was removed from the list of "objects presenting a threat".