Every hour from power-on the guest machine changes time, but I have disabled time sync in VM settings. It changes time because I have host and guest set to different timezones. I'm aware that this causes problems when using time sync, but I'm trying NOT to use time sync. I have uninstalled Parallels Tools, but still it happens. Why? I have roughly 30 machines, a mixture of native PC, VMWare VMs and Parallels VMs, and this symptom is only occurring on the 4 Parallels VMs I am running. I'm aware I'm running an older version of Parallels, PD9. I don't need an "upgrade and see if it goes away" answer. I already know it goes away if I use VMWare. I'd like to make my current installation work correctly. Can anyone shed any light on how host-guest time synchronisation is achieved? I was confident that it used Parallels Tools, but now I'm not so sure. Is there another service I can disable, a file I can rename etc? Or is it completely managed from outside the guest? Perhaps the Parallels software manipulates the VM from outside.