At this point , I think it’s quantum that has collapsed at a particular point of time and people just don’t remark (just studied quantum computing). Let say a,

At this point , I think it’s quantum that has collapsed at a particular point of time and people just don’t remark (just studied quantum computing). Let say a, b, c, d are successive points in time and c is when the protagonist decides to go back in time and he revert back in b. The whole b-c timeline collapses due to the simultaneous time directions.