It is called the Time Traveler's Paradox. In which a scientist creates a Time Machine and kills their younger self. So now a man who should not- can not- exist, somehow does. That is the Paradox, and Paradoxes are impossible.
2012
2019
1999
1917
2005
2024
2007
1951
2015
2001
1962
2006
1965
2013