title: Generate icalendar file to update existing event
body: <p>I've created the following iCalendar file to generate the initial event</p>
  <pre><code>BEGIN:VCALENDAR
  VERSION:2.0
  PRODID:icalendar-ruby
  CALSCALE:GREGORIAN
  METHOD:PUBLISH
  BEGIN:VEVENT
  DTSTAMP:20170529T184713Z
  UID:call_286@foobar.dev
  DTSTART:20170427T160000Z
  DTEND:20170427T163000Z
  DESCRIPTION:A test call
  SEQUENCE:7
  STATUS:CONFIRMED
  SUMMARY:A test call
  URL:http://foobar.dev/calls/286
  BEGIN:VALARM
  ACTION:DISPLAY
  TRIGGER:-PT15M
  DESCRIPTION:Starting in 15 minutes - A test call
  SUMMARY:A test call starting in 15 minutes
  END:VALARM
  END:VEVENT
  END:VCALENDAR
  </code></pre>
  <p>This event is properly imported into OSX's Calendar (v 9.0) with all the correct details and Sync'd to Google Calendar.</p>
  <p>I then update the event and generate an updated iCalendar file, keeping the <code>UID</code> the same and increment the <code>SEQUENCE</code> as per the <a href="https://www.rfc-editor.org/rfc/rfc5545#page-141" rel="nofollow noreferrer">specification</a></p>
  <pre><code>BEGIN:VCALENDAR
  VERSION:2.0
  PRODID:icalendar-ruby
  CALSCALE:GREGORIAN
  METHOD:PUBLISH
  BEGIN:VEVENT
  DTSTAMP:20170529T185549Z
  UID:call_286@foobar.dev
  DTSTART:20170427T153000Z
  DTEND:20170427T155500Z
  DESCRIPTION:A test call
  SEQUENCE:8
  STATUS:CONFIRMED
  SUMMARY:A test call
  URL:http://foobar.dev/calls/286
  BEGIN:VALARM
  ACTION:DISPLAY
  TRIGGER:-PT15M
  DESCRIPTION:Starting in 15 minutes - A test call
  SUMMARY:A test call starting in 15 minutes
  END:VALARM
  END:VEVENT
  END:VCALENDAR
  </code></pre>
  <p>I then import this event into OSX's Calendar and my original event disappears from the calendar completely. It doesn't update at all just completely disappears.</p>
  <p>When I look at Google Calendar the original event is still there in the exactly the same place as per the initial time schedule.</p>
  <p>What am I doing wrong that the event is not updating?</p>
  <p><strong>Update:</strong> This question is not a duplicate of <a href="https://stackoverflow.com/questions/275759/update-an-event-in-outlook-2007-with-an-icalendar-file">Update an event in Outlook 2007 with an iCalendar file</a> or <a href="https://stackoverflow.com/questions/45453/icalendar-and-event-updates-not-working-in-outlook">ICalendar and event updates not working in Outlook</a> or <a href="https://stackoverflow.com/questions/275759/update-an-event-in-outlook-2007-with-an-icalendar-file">Update an event in Outlook 2007 with an iCalendar file</a> as this question related to <strong>OSX's Calendar (v 9.0) application</strong> and subsequent syncing with <strong>Google Calendar</strong> and <strong>not Outlook</strong>. I have tried the approaches described in answers to those questions but I get exactly the same behaviour as described above.</p>