Yesterday I came in to install updates on all our servers.  I updated every server except our #2 DC.  No particular reason, I just forgot.

I walked into the building this morning and sat down at my desk only to notice that my computer clock (along with everyone else’s) is exactly 1/2 hour off GMT-5 time.  The only clock that isn’t off is the one domain controller that syncs its time externally, which is not the aforementioned #2 DC.

After installing updates on the forgotten DC and rebooting, everything seemed to go back to normal.  In fact, all of the PCs on the network synced back to the correct time almost instantly.

Aside from “Patch your Domain Controllers simultaneously,” I don’t know what the moral of this story is, but it’s definitely an interesting issue.