Even though you've unchecked the time synchronisation checkbox in VMware Tools, synchronisation may still occur. Particularly when a certain action is performed, such as a power-off/power-on, suspend/resume, snapshot handling, etc., time synchronisation will still occur.
To complete disable time synchronisation, even during the events mentioned, you have to add additional parameters to the VMware VM configuration. There are two ways to do this.
Note that you need to have the machine powered off before you can do these changes.
Use a text editor to directly edit the .vmx-file, adding the required parameters:
tools.syncTime = "0" time.synchronize.continue = "0" time.synchronize.restore = "0" time.synchronize.resume.disk = "0" time.synchronize.shrink = "0" time.synchronize.tools.startup = "0" time.synchronize.tools.enable = "0" time.synchronize.resume.host = "0"
Note that 0 means "disabled" and 1 means "enabled;".
For ESX and ESXi, you can use the vSphere client to add the parameters.
Power off the machine, then edit the VM's settings. On the Options tab, look for General (under Advanced). Click the Configuration Parameters button, then start adding rows:
Note that the parameter tools.syncTime will disappear as soon as you've added it and click OK. This is normal, the .vmx-file will contain the parameter as tools.syncTime = "FALSE"