We have deployed a number of distributed vSphere hosts all of which are succesfully syncing to a central NTP service, but the Centos hosts time is drifting badly. The latest version of VMware tools is installed and the timesync enabled (checked vmx config file) and the service is running.
If we restart the vmware-tools service the time is corrected but it appears that the vmware-tools timesync is then not running on a regular basis as the VM's are between 10-60 minutes ahead of the host / real time. Reading knowledge base articles they do make reference of time drift, but all items are configured and correct we need the time sync to work correctly.
Search for KB related to Linux time sync. It depends on the os version, bitness, clock too fast or too slow. A change in the kernel boot parameter will help. Also ntpd is more reliable than Vmware Tools on a Linux VM in my experience.
Since I'm lazy today:
Use the divider=10 clocksource=acpi_pm kernel parameters as per http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=100642....
Also, make sure to use the correct HAL.