title: How to determine original recurring event id of a series in Google Calendar API?
body: <p>I want to group all recurring single events under the same parent. </p>
  
  <p>The "recurringEventId" attribute is used for that. But that approach only works until the user changes anything in the series. For example he extends the series or he changes the time, and when saving chooses the option to apply the changes to "This and the following events". In that moment, Google seems to create a complete new, independent series with a new recurringEventId. </p>
  
  <p>Is there any way to know the original recurring event id of the events or any attribute which links the two series with each other?</p>
  
  <p>Here is an example. Event of original series: (partial json)</p>
  
  <pre><code>{
    "id": "13jq1025j8h1720v879uppupta_20200407T110000Z",
    "summary": "Recurring Fry",
    "start": {
      "dateTime": "2020-04-07T13:00:00+02:00",
      "timeZone": "Europe/Zurich"
    },
    "end": {
      "dateTime": "2020-04-07T14:00:00+02:00",
      "timeZone": "Europe/Zurich"
    },
    "recurringEventId": "13jq1025j8h1720v879uppupta",
    "iCalUID": "13jq1025j8h1720v879uppupta@google.com"
  }
  </code></pre>
  
  <p>Event of the series after changing an event and saving the changes for "this and the following event"</p>
  
  <pre><code>{
    "id": "ru2of0r8ph60qu5jedlgpbstcv_20200408T120000Z",
    "summary": "Recurring Fry",
    "start": {
      "dateTime": "2020-04-08T14:00:00+02:00",
      "timeZone": "Europe/Zurich"
    },
    "end": {
      "dateTime": "2020-04-08T15:00:00+02:00",
      "timeZone": "Europe/Zurich"
    },
    "recurringEventId": "ru2of0r8ph60qu5jedlgpbstcv",
    "originalStartTime": {
      "dateTime": "2020-04-08T14:00:00+02:00",
      "timeZone": "Europe/Zurich"
    },
    "iCalUID": "ru2of0r8ph60qu5jedlgpbstcv@google.com"
  }
  </code></pre>