openapi: 3.0.0

info:
  version: 1.0.0
  title: Native date formats in YAML

paths:
  /foo:
    get: 
      description: Has date without quotes
      responses:
        '200':
          description: Ok
          content:
            application/json:
              schema:
                type: object
                properties:
                  without-quotes:
                    type: string
                    format: date
                    example: 1999-11-31
                  with-quotes:
                    type: string
                    format: date
                    example: "1999-12-31"