How can I stop this? Boss is giving me a hard time about military matters.?

Weather it's in your orders or not, I would suggest you ask you 1SG or have him direct someone from your chain of command speak to him/her about your situation. It's never good to get started on the wrong foot with your military career. If need be, get it in writing from your unit that you are required to show at a time, and remind your boss that if you fail to show at a time, it is missing formation/ movement, and that you will fail to follow a lawful order. He/She cannot put up a fight with the law.