Sorry for the late reply.
If it helps, I'll explain exactly what happened to me.
We have had 2 Cisco C210 M2 servers running XCP since release (and Xen prior) as a single pool. This had worked for around 3 years. Never once saw the time error.
A few months ago we set up 2 R720 with XCP 8 as a single pool. Once it was all running, I was running VM's on them just fine for around 2 weeks. Then for some reason, 1 of them completely disappeared from the pool. It was still there, the iDRAC was still accessible. SSH was accessible to the server. When SSHing in and looking at the console, it reported there was no network cards or storage. It seems completely broken but was all still functioning. The VM's that were running on it had moved over to the second server. Rebooted the machine and it was back to normal.
Can't be precise as I hadn't written it all down, but I remember looking thru the logs (via XO) and seeing something about XOA time not matching something time...
I didn't take much notice at that point, and within 24 hours the Second server did exactly what the first server did.
After that, I saw the same error messages again regarding time. I then double-checked the bios time on the servers (both set to UTC) and both were correct. I then went into xsconsole and saw there that neither has the timezone set, so I set them, and also set both NTP settings up. For a few weeks, they seemed to start behaving.
I had to run some XCP patches on them recently and in the process (doing the install, reboot, restarting toolstack etc) I did notice that for a moment XO reported the time error again. My guess is in this instance it had to do with the tool stack restarting. Once updates were complete, all returned to normal and I haven't seen the time error since (yet).
I hope the above information helps.