This can now be done using VBoxManage utility. It's a command-line tool, which is available in the Virtualbox install folder in Windows or in ~/Library/Virtualbox on Mac. Turn off time syncing:vboxmanage setextradata [VMname] "VBoxInternal/Devices/VMMDev/0/Config/GetHostTimeDisabled" "1" Turn it back on:vboxmanage setextradata [VMname] "VBoxInternal/Devices/VMMDev/0/Config/GetHostTimeDisabled" "0"