VirtualBox Guest Additions date settings

If you need to change the date settings in a VirtualBox machine use the following command in the cmd/terminal:

Offset in miliseconds:

VBoxManage modifyvm <vm name> -biossystemtimeoffset <offset in milliseconds>

6 months in msec:

15768000000

Example (minus 6 months from current date):

VBoxManage modifyvm WindowsXP --biossystemtimeoffset -15768000000