I've researched this heavily. All attempts to get a win2k8R2 standalone server (acting as the PDC), to use an external time source fail. No GPOs are in place or configured for time or NTP
UDP 123 is open

I can successfully monitor my external time source via
w32tm /monitor /computer:talk.mtnlion.com
tock.mtnlion.com[204.13.164.130:123]:
    ICMP: 23ms delay
    NTP: -78.1962934s offset from local clock
        RefID: tick.ucla.edu [164.67.62.194]
        Stratum: 2

and using:
w32tm /stripchart /computer:tock.mtnlion.com /dataonly
Tracking tock.mtnlion.com [204.13.164.130:123].
The current time is 9/6/2015 2:33:43 PM.
14:33:43, -78.1976906s
14:33:45, -78.1998127s
14:33:47, -78.2007549s

more info:
1. MS Fixit tool 50395 finishes with "..failed process"
2. Starting over using
net stop w32time
w32tm /unregister
w32tm /register
net start w32time
C:\Users\Administrator>w32tm /config /manualpeerlist:"tock.mtlion.com,0x8 time.windows.com,0x9 0.pool.ntp.org,0x8 0.north-america.pool.ntp.org,0x8" /syncfromflags:manual /reliable:yes /update
w32tm /resync

/resync yields:
The computer did not resync because no time data was available.
and Event viewer has Event ID 47

then when I /query /status I get:
Leap Indicator: 0(no warning)
Stratum: 1 (primary reference - syncd by radio clock)
Precision: -6 (15.625ms per tick)
Root Delay: 0.0000000s
Root Dispersion: 10.0000000s
ReferenceId: 0x4C4F434C (source name:  "LOCL")
Last Successful Sync Time: 9/6/2015 1:50:43 PM
Source: Local CMOS Clock
Poll Interval: 6 (64s)

I don't know what would cause the server to not use the configured external source and revert to the CMOS clock. No firewall issues. No GPOs are configured. No DNS issues. I see in the w32tm debug log files reference to "no response" as if it were a DNS issue but it can't be because it is translating the name to an IP and /monitor and /stripschart work from the prompt. I need some help fixing this! Workstations eventually cannot authenticate because time sync issues with the server caused by accumulated time differences.

 a portion of debug/log files from w32tm.

----------------------------------

...

151458 21:56:28.0146328s - 0 Age:5 Ofs:+00.0000000s Dly:+00.0000000s RDly:+00.0000000s Dsp:16.0000000s RDsp:00.0000000s Pnt:00.0044452s Dst:16.0044452s FDsp:15.7500000s
151458 21:56:28.0146328s - Logging information: NtpClient has not received response from server 0.pool.ntp.org,0x8 (ntp.m|0x8|0.0.0.0:123->129.250.35.251:123).
151458 21:56:28.0146328s - Logging information: NtpClient: No response has been received from manual peer 0.pool.ntp.org,0x8 (ntp.m|0x8|0.0.0.0:123->129.250.35.251:123) after 8 attempts to contact it. This peer will be discarded as a time source and NtpClient will attempt to discover a new peer from which to synchronize. Error code: 0x0000005C
151458 21:56:28.0146328s - Reachability:  removing peer 0.pool.ntp.org,0x8 (ntp.m|0x8|0.0.0.0:123->129.250.35.251:123).  
151458 21:56:28.0146328s - *** Manual Peer timed out - other paths remain.
151458 21:56:28.0146328s - Polling peer 0.pool.ntp.org,0x8 (ntp.m|0x8|0.0.0.0:123->216.218.254.202:123)
151458 21:56:28.0146328s - Sending packet to 0.pool.ntp.org,0x8 (ntp.m|0x8|0.0.0.0:123->216.218.254.202:123) in Win2K detect mode, stage 1.
151458 21:56:28.0146328s - PollIntervalChange(0.pool.ntp.org,0x8 (ntp.m|0x8|0.0.0.0:123->216.218.254.202:123)): adjust: (--) -> 3
151458 21:56:28.0146328s - No response from peer 0.pool.ntp.org,0x8 (ntp.m|0x8|0.0.0.0:123->216.218.254.202:123).
151458 21:56:28.0146328s - 5 Age:3 Ofs:+00.0000000s Dly:+00.0000000s RDly:+00.0000000s Dsp:16.0000000s RDsp:00.0000000s Pnt:00.0067376s Dst:16.0067376s FDsp:08.0000000s

...

Dave