I was using a utility called AD Tidy to show me the last logon dates of my users so I could remove unused accounts, however 4 users have a last logon in the future. We have 4 domain controllers and the one common factor is these 4 users all authenticated against the same domain controller, where all the others were on different ones. I logged into the problematic domain controller and the time and date are correct. What could possibly be the cause of this? It isn't affecting the users to my knowledge, but it is an issue I'd like to resolve.