It's pretty common that most stores open at noon on sundays, exceptions to walmart and grocery stores that I can think of.
So why are you waiting in the parking lot of my store at 10 when I get there to start opening? The hours are displayed very clearly on the door, go get yourself a coffee or something.
Oh, you want to shop now? Sorry ma'am we aren't open for business until noon.
Oh, you don't have time to wait until noon? Well, I'm sorry but I can't let you in the store, it's against policy and a security issue.
Oh, you don't give a fuck about my policies or security? Well, I'm sorry to hear that, but I'm still not letting in.
Oh, you want to speak to my manager? You're looking at her.
You know a really quick way to ruin a sunday? Try and force your way past a employee (me) to get into the store to do your shopping, and in the process knock said employee down and cause her to dislocate her shoulder and get cut up.
Even the fucking police officers didn't believe my story but she was still frothing at the mouth with her indignant "Customer is always right" mentality and they hauled her off.
So to all of you, please respect the store hours, both the times for opening and the times for closing.