> Adding timestamp to JSON . . .

What are you talking about? JSON is a format for exchanging data of any kind. It doesn't have types beyond a set of primitives to that it can remain as a _notation_ that allows you to pass any type you define and want to send.

Nothing is stopping any library or language from implementing an object or String for dates or times (or both) and tons of them have done so.

It wouldn't be JSON's place at all to start defining anything like that.