Assert local time is correct

[mkalinin]

To Do

Beacon chain processing is a time critical process. Hence, local clock time should be verified against some source on the Internet. User should be notified if local clock time differs from the global one.

[Nashatyrev]

Apache NTP client: https://commons.apache.org/proper/commons-net/

[zilm13]

I think app should have it's own time or maybe choice in config between own and system.
Plus time correction is not start only task. If your client is running for a days, it's definitely a regular job.