Next year I will be a junior taking AP Calc AB, AP Chem, AP Stats (May change to AP Bio), IB English HI 1, IB History HL 1, and IB French HL 1. My high school is on a seven period schedule, so I am considering taking an early release and not filling in the extra spot with another class. How will this affect my college admission (Dream schools are Stanford and UCLA)? Please provide any personal experience if you took an early release (or late start) and how you felt it accepted your admissions. Thank you 
Obviously those schools want you to take the most rigorous schedule you can, but I wouldn’t necessarily say that taking an early release would kill your chances. If you decide to do so and it becomes a problem, you can always make up for it by saying that you used that free time to do extracurricular activities or some independent study of some subject.
Also, perhaps you should consider how obvious your choice will be to those schools. For example, my first period opt out doesn’t show up on any transcripts, so it isn’t glaringly obvious that I chose to sleep in everyday as opposed to taking another class.