One of our domain controllers clock drifted way out of sync with the rest of the network (thanks to me forgetting to turn off VMWare's time synchronisation), which caused a whole bunch of servers to lose their ability to authenticate, given that kerberos requires close time synchronisation between servers.
I manually logged onto it, fixed the clock to the correct time, but it took more than 15 minutes for authentication to start working again (this was a problem, as it was a bunch of terminal servers with people waiting to start their work).
Further information: While the clocks were out of sync, users were getting "there is a time difference" message and their logon was refused. However, after syncing the time, this message went away, but nobodies passwords would work, they were just rejected as invalid. Waiting 15 minutes made them all work again.
In case this happens again, how can I speed up the time taken between putting the clocks back in sync and having normal authentication again?