I didn't experience any either but on anniversary dates of PTSD related things that I remember or really bad times I had my mood can get irritable and more anxious than usual and such and I start behaving irrationally and strangely and getting hypervigilant, tearing people apart for perceived threats in a misguided bid to defend myself when there probably weren't any, and some other things most likely. My symptoms also get exacerbated.
I find distraction from the triggers helps dramatically.
I know on the anniversary of my mom's death, I actually try to do fun things if at all possible. I know she wouldn't want me sitting around feeling sad and so I try really hard to be happy. The good thing is my husband's birthday is the day before her anniversary, so I focus on his brithday more. I say that is a sign he was meant to be in my life to give me something good to focus on at that time of year.
I think the people who died that day would want us all to remember the good things about life and to celebrate life instead of death. I don't know if you are spiritual or not or how able you are to get out and do things, but maybe go do positive things on that day and spend time in a happy place it would help you.