title: Single day all day appointments in .ics files
body: <p>I'm creating an ics file using ASP.NET for importing holiday into Outlook 2007 and trying to set the all-day-event flag. This works fine on multi-day holidays, but for single days, it doesn't seem to be registering, I just get a 'singularity holiday' booked from midnight to midnight.</p>
  
  <p>According to <a href="http://msdn.microsoft.com/en-us/library/ee158730.aspx" rel="noreferrer">MSDN</a>, setting the start and end times to 00:00 should be enough to do this. I've also tried using the X-MICROSOFT-CDO-ALLDAYEVENT and X-MICROSOFT-MSNCALENDAR-ALLDAYEVENT flags, but they don't seem to have any effect.</p>
  
  <p>Can anyone see where I'm going wrong? I've included sample ouput below.</p>
  
  <pre><code>BEGIN:VCALENDAR
  PRODID:-//Microsoft Corporation//Outlook 12.0 MIMEDIR//EN
  VERSION:2.0
  METHOD:PUBLISH
  X-MS-OLK-FORCEINSPECTOROPEN:TRUE
  BEGIN:VEVENT
  CLASS:PUBLIC
  DESCRIPTION:HOLIDAY\n
  DTEND;VALUE=DATE:20090727
  DTSTAMP:20091111T000000Z
  DTSTART;VALUE=DATE:20090727
  LAST-MODIFIED:20091111T000000Z
  PRIORITY:5
  SEQUENCE:0
  SUMMARY;LANGUAGE=en-gb:HOLIDAY
  TRANSP:OPAQUE
  X-ALT-DESC;FMTTYPE=text/html:HOLIDAY
  X-MICROSOFT-CDO-BUSYSTATUS:OOF
  X-MICROSOFT-CDO-IMPORTANCE:1
  X-MICROSOFT-DISALLOW-COUNTER:FALSE
  X-MS-OLK-ALLOWEXTERNCHECK:TRUE
  X-MS-OLK-CONFTYPE:0
  X-MICROSOFT-CDO-ALLDAYEVENT:TRUE
  X-MICROSOFT-MSNCALENDAR-ALLDAYEVENT:TRUE
  END:VEVENT
  END:VCALENDAR
  </code></pre>