title: When recurring id is generated with format previous_event_id+_R+date
body: <p>Normally, this is the format of a recurring event ID generated by Google:
  qmjtng94k5mgge24890nmoasts (26 character alphanumeric)</p>
  
  <p>In some cases, we see that the recurring event ID generated is of the format:
  qmjtng94k5mgge24890nmoasts_R20160823T180000</p>
  
  <p>I want to know when this kind of event Id is generated ?
  Specifically, when is a recurring event ID generated with the underscore, capital R, date suffix and the same previous eventId prefix?</p>