Is there a command to get the
DateTime of when
bitcoind last received a block?
No, there isn't.
getblockcount can only get the number of blocks in the best chain, but not the last received block.
You might need to write a new rpc to get the last received block.
First, add a new data structure in main.cpp and record blocks received order in
Second, write a rpc to print out that data structure.
If you mean the number of blocks in the entire chain,
getblockcount gives you that.
getblockchaininfo also both contain "blocks" in their reply. The latter also includes "headers", which should show you a higher number than "blocks" when bitcoind has not caught up yet but has heard about a newer block.