Virtualbox (or its Guest Additions) have this annoying habit of automatically keeping the clock in sync with the host, regardless of the settings that one tries to implement within the guest itself. For example, in a Windows 7 guest that I’m trying to use for consistent screenshots I need to set the clock to specific dates. However, as soon as I set it, Virtualbox changes it back.
Here’s how to change it:
vboxmanage setextradata “<vmname>” “VBoxInternal/Devices/VMMDev/0/Config/GetHostTimeDisabled” “1”