If you run VirtualBox you may eventually run into problems with the time or time sync within your VM guest. You can run this command on the host to disable time sync:
vboxmanage setextradata <vmname> “VBoxInternal/Devices/VMMDev/0/Config/GetHostTimeDisabled” “1”
Just replace <vmname> with the name of your guest. On Windows hosts, you’ll need to change the command to “VBoxManage”.
You will most likely want to set the client to sync with a time server after this. On Windows clients, just double click on the time and go to the Internet Time tab. Check the box and choose time.nist.gov (better reliability).
I needed to solve this because QuickBooks Pro 2000 complains about the system time being changed continuously while in multi-user mode.
I found this simple VirtualBox time sync tip in a post titled Synchronize a Virtualized Domain Controller with External Time Servers.