I had an issue similar to what the OP asks about...Purchased at ticket between 1 am and 2 am EST but it showed as purchased two hours earlier, so the night before. The affected the cancellation window.

What I was told in the end is that the time stamp for the ticket purchase is determined by the CREDIT CARD COMPANIES computer!

Yeah doesn't make a lot of sense to me either and I don't know if that is true...but just relaying what I was told...