I had JMC running on JDK 10 and dumped the last 5 minutes of the flight recording. After doing this twice (not an exact reproducer, sorry for that), I see a recording listed as "Snapshot" in JMC. That recording has a very strange start time (not 2017-10-30 as expected, but 292278994-08-17 08:12:55). This corresponds to 9223372036854775807 ms, according to JMC. If I look in the json produced by the reference parser, I see the following values:

{
      "name": "com.oracle.jdk.ActiveRecording",
      "typeId": 1634,
      "startTime": "2017-10-30T09:32:53.360024479Z",
      "duration": "PT0S",
      "values": {
        "startTime": 463718693704,
        "duration": 0,
        "eventThread": {
          "osName": "Worker-4",
          "osThreadId": 78407,
          "javaName": "Worker-4",
          "javaThreadId": 62,
          "group": {
            "parent": {
              "parent": null,
              "name": "system"
            },
            "name": "main"
          }
        },
        "stackTrace": null,
        "id": 1,
        "name": "JMC_Default",
        "destination": null,
        "maxAge": 9223372036854775807,
        "maxSize": 104857600,
        "recordingStart": 1509355780868,
        "recordingDuration": 9223372036854775807
      }
    }, {
      "name": "com.oracle.jdk.ActiveRecording",
      "typeId": 1634,
      "startTime": "2017-10-30T09:32:53.360040434Z",
      "duration": "PT0S",
      "values": {
        "startTime": 463718731996,
        "duration": 0,
        "eventThread": {
          "osName": "Worker-4",
          "osThreadId": 78407,
          "javaName": "Worker-4",
          "javaThreadId": 62,
          "group": {
            "parent": {
              "parent": null,
              "name": "system"
            },
            "name": "main"
          }
        },
        "stackTrace": null,
        "id": 6,
        "name": "Snapshot",
        "destination": null,
        "maxAge": 9223372036854775807,
        "maxSize": 0,
        "recordingStart": 9223372036854775807,
        "recordingDuration": 9223372036854775807
      }
    }

Is this snapshot recording event necessary to produce an event for? Should it be visible and used for something, or is it only an artifact of some sort?