Windows Server 2012 R2 PDC has no internet time tab

Question

Clients on our domain get their time from the PDC, but the time on the PDC keeps on drifting forward about 5 minutes every few days. All the solutions I search say to log on to the PDC and change the Internet Time tab to sync with an external source. I've seen others that use powershell w32time commands to set external time servers. I've tried these and they have no effect.

Problem: Our PDC has no Internet Time tab. Powershell w32time commands don't work.

Question: How do I set the time on my PDC when it's missing the Internet Time tab and is unresponsive to w32time commands?

Thanks!