Testing an External NTP Server

First off, NTP uses port 123. That was the first thing I checked when trying to telnet to one of the pool.ntp.org servers. Seems most NTP server ignore the telnet command.

Then I thought I'd use net time, but it has been deprecated in Windows 7 in favor of the newer w32tm command.

There's a litany of switches to use with it, but the /monitor /computers:server are the ones you want.

And using the command: c:\w32tm /monitor /computers:time.nist.gov
You will get the following output, showing it works:

time.nist.gov[64.250.177.145:123]:
    ICMP: 59ms delay
    NTP: -0.1402919s offset from local clock
        RefID: 'ACTS' [0x53544341]
        Stratum: 1

You can find a huge amount of popular public NTP servers at NTP.org