This how-to will be using the Flex interface (the flash version)
- Log into your vcenter appliance
- Expand your hosts and select one of them
- Click on Configure
- Scroll the list inside the configuration section, expand System and choose Time Configuration
- Click Editat the top right
- Click the radio button Use Network Time Protocol
- Choose Start and stop with host
- Paste the following IP's
129.6.15.28, 129.6.15.29, 129.6.15.30
- Click Start
- Click OK
Repeat these steps for each host.