We disable time sync (and in some cases for the incorrect time for testing a past or future time) by using VCO to set some advances VM properties before the VM is started (we catch it a instatiate and set the settings) - we have to use some vCenter API calls to set these values.
Document with some time settings.
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1189
Some PowerCLI:
http://professionalvmware.com/2009/10/time-is-marching-on-disabling-timesync-completely/
Hope that gets you going - messing with the time settings is not really a good default behavior so it does seem VMware makes it a little complex to do - but if you need to a way does exist.
