Administrators that's got some experience in running Linux guest operating systems in virtual machines, may know that the time of the guest OS can drift by several hours per day. Normally, in my experience the time in the guest OS runs too fast. This can have serious implications on some services that these servers provide, such as Mail/Spam relays and web servers.
VMware has now released a very good KB article on best practises for Linux Guest OS time keeping, with a table of kernels and their parameters.
The KB article is a must read for those who have Linux guests. You can find VMware KB Article 1006427 here