I don't have a zNC to test on, but it looks like you need to use echo -mt $+ $msgstamp
If you need to have an alias pull double duty for normal vs znc connections, you can have logic to use 2 different echoes. I'm guessing $left($nick,1) == $chr(42) might do it?
Maroon thank you very much for the help. Your solution solved the problem.
With this solution on znc connections or the rest, your solution presents the server-time or local time.