I am having the same issue, however it is only affecting entried for this week.....Weird. Even reoccurring entries are wrong this week, but right from there on out.
Can anyone else confirm if this is the same behavior that they are experiencing, or is it your whole calendar that is off by an out?
Also, I called HTC, he had me run through toggling Time zones and forcing a calendar sync, none of that worked and he said he had no idea. He also stated that Tmobile had a similar problem on thier android phones, and if you called customer service, they had a fix right there before you even talked to and agent. Maybe Sprint has a similar issue, who knows. I will call them next and report back.
Update: Spoke to Sprint CS and they have no idea what is causing the issue, but did acknowledge tjat there were many people calling in with the same issue.