Very small 5 user system with 1 Hyper-V 2012R2 host & 2 WS2012 HV guests, one of which is the only DC for the domain, and thus, the PDC Emulator. (A physical DC is beyond their budget.)
HV Time Service is disabled for the DC guest. On the DC I ran the WS32TM command for setting an authoritative time source (0.pool.ntp.org, 1.pool.ntp.org & 2.pool.ntp.org) and it returns the time servers when I use the /QUERY /SOURCE command. There are no Group Policies or registry settings or any other customization of the time server...it's completely default except for setting the external NTP server and disabling HV time service.
When first set up time was set accurately. But after a while (don't know how long or the trigger) it drops back to 20 minutes slow. And it's ALWAYS 20 minutes. Not 19, not 21, 20 exactly.
Another W32TM /RESYNC and it catches up again.
All computers in the domain correctly sync to the DC so there are no auth problems...the problem is the time is off by 20 minutes.
I created a Scheduled Task to run W32TM /RESYNC every 30 minutes on the DC, and I'm hopeful that will avoid the problem. But I would like to understand why this is happening because we have other, similar systems where this is not occurring and I can't figure out what the difference is.
TIA
Jeff