Keep Your Mac and Windows Boot Camp Clocks in Sync

If you manage dual-boot Macs, or even just have your own dual-boot Mac, you may have noticed the annoying tendency of your Mac clocks to be incorrect when you reboot from Windows into Mac OS. This occurs because the Windows internal clock uses the local time zone to manage its time while Mac OS internal clock uses GMT.

As posted in various forums and sites, the solution is to modify the Windows Registry as follows.

  1. Launch regedit.exe.
  2. Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation.
  3. Create a new key called RealTimeIsUniversal (case-sensitive!)
  4. Give the key a DWORD Value (displays as REG_DWORD) of 1.

If you’re not comfortable modifying the registry by hand, I’ve created a registry patch file that, when double-clicked in Windows, will make the modification for you. (You can verify the contents of the patch by opening it in Notepad.) Download the patch here.