So I typed out a long version of this, but then accidently hit Cmd+Q, so now I'm doing a short version. My Mac mini, running the latest OS X 10.9.1, insists that it belongs in the future by about roughly 30s. This time discrepency manifests itself primarily when watching tweets stream in on Tweetbot, with freshly posted ones come in with a timestamp of 20-40s earlier (varies with each resync). Opening Date & Time Preferences forces the computer to resync with Apple's time server (I tried the NIST server as well with no luck on this issue, as well as disabling server sync entirely), which fixes the issues for a few hours before it changes again. I have NO idea what could cause this, and it's been going on long enough for me not to be able to deal with it anymore. What gives?