Does anyone know which port(s) are required to be left open to enable WHM's option to "sync time with time server"? I initially assumed UDP 123 but that doesn't do the trick. With my firewall up the time doesn't update. With my firewall down for a couple of seconds it updates without a problem.
Thanks for any advice.

Usually its port 37, but it may be different on your box. Give it a go!
~Equinox