I've read that alarm clocks are authorized. I'm going to assume that's true, but only after Indoc week. My time at VT showed me that the breakdown phase of military training is best done when none of the candidates (in my case, cadets) have a freaking clue what time it is.
Correct assumption?
A non-radio alarm clock IS permitted from day 0 on and, moreso, is REQUIRED. You need to be up WELL before Reveille, and that is how you do it. Looking at your alarm clock in the morning is one of the only (or possibly the only) time you'll know what time it is during the day until well into OCS.