In the original timeline, Marty shows up at 1:16. Events unfold there over the next 15 minutes or so until the Libyans catch up with Doc (right around 1:32). In the timeline where Marty is returning from 1955, he does attempt to arrive early and sets the time circuits for 1:24am. Unfortunately, the Delorean stalls on him and he’s forced to run from downtown Hill Valley to Lone Pine Mall in the suburbs, which apparently takes about 9 minutes. By then, it’s too late.