How can I tell how old my newt is?

-I have a newt, it was found before my brother was born 20 years ago, it has never been replaced, every time we try to get it a friend, the old newt bites chunks out of it, I just want to know if there's any simple way to get a rough estimate as to how old it actually is, as we have no idea, as it was found on my grandparents driveway 20 years ago, but we have no clue how old it was at the time.Its hard to tell how old a newt is, its basically impossible.

Sorry to tell you, but they aren't like turtles where you can count the rings on their shells.

And please note: Newts are territorial, that probably why it keeps killing other.when were they born? ask if you got them from a pet store, or if you raised it since it was born just take that date and take today's date and figure it out