When do incoming freshmen enroll in classes?

So how does it work with adjacent class lectures? In the example of Math 1B and CS61A, IIRC the 12pm-1 class is at Valley and the 1pm-2 class is in Wheeler. A little bit of a hike. Do they start on time in the lectures? I have a feeling that after 3 years of grueling 7am start classes, my kid is going to balk at taking an 8am Calc class lol.