When installing Couchbase server, there should be a reminder that all servers should implement NTP

We currently document that – 

In a multi-cluster environment, it is important for all the nodes in the cluster to have the same time from a global perspective. In other words, all the nodes must synchronize with the same reference server and time.

We also note that –

Correct time synchronisation is important in Couchbase Server for Expiry behavior and to maintain accurate synchronicity in timestamp-based conflict resolution (see Time Synchronization)

So, when users are installing the Couchbase Server, we should be reminding them of the above two pieces of information and to enable/implement NTP on the machines where Couchbase Server is installed to ensure correct functioning of Couchbase Server features within a cluster and across clusters.