If you're not reading the forum for the VMware VI Toolkit Beta you are missing out on just a goldmine of useful information. Take this post from LUCD. This will allow you to query the ESX host for it's current time. This another one of those instances where there is no applet in the toolkit to do this so you hook into the API to get the information.

Get-VIServer -Server <Replace with yourServer Name>

http://Reflection.Assembly::LoadWithPartialName("vmware.vim")

$svcRef = new-object VMware.Vim.ManagedObjectReference

$svcRef.Type = "ServiceInstance"

$svcRef.Value = "ServiceInstance"

$serviceInstance = get-view $svcRef

$datetime = $serviceInstance.ServerClock

*
Write-Host $datetime

*