Time Sync without public server

I have 2 servers in a cluster in a non-public subnet which cannot get to a public time server.

I want the 2 in the cluster to sync in time to each other without the use of a public time server.

Environment
Cluster 2 servers running Windows 2000 advanced server. Private network.

I have 2 locations and both are private zones with Oracle Cluster and Windows Cluster config.

Alston Davis