How to get the time when a block is received at a node?
I don't believe this is exposed via the JSON-RPC API.

The easiest method would likely be to have a program monitoring debug.log and look for the best height update messages - they will be a few milliseconds off, since I believe those are only logged after block validation has succeeded, but it is likely the closest you can get to a per-node block receipt time, at least without monitoring the network traffic.