Convert UNIX epoch to local time

Elastic Stack Logstash
5 
{
  "bkki-2017.04.07" : {
    "mappings" : {
      "logs" : {
        "submission_time" : {
          "full_name" : "submission_time",
          "mapping" : {
            "submission_time" : {
              "type" : "date"
            }
          }
        }
      }
    }
  }
}


  "bkki-2017.04.07" : {
    "mappings" : {
      "logs" : {
        "delivery_time" : {
          "full_name" : "delivery_time",
          "mapping" : {
            "delivery_time" : {
              "type" : "date"
            }
          }
        }
      }
    }
  }
}