I guess my point was something like an ISO 8601 date would be beyond the scope of a built in data type given JSONs philosophy of a minimal spec. It’s up to the end user to define types like that.

The below type definition (TS) fits the ECMA schema for JSON:

    type JSON = 
      string |
      number |
      boolean |
      null |
      JSON[] |
      {[name: string]: JSON}