What I did was to replace the Start Time - End Time with Start Time - Duration on the "Add Event" page. The duration field is a dropdown box. Here are the first few entries.

<option value="1440">All Day</option>
<option value="0">Note (No Duration)</option>
<option value="30">30 minutes</option>
<option value="60">1 hour </option>
<option value="90">1 hour 30 minutes</option>
<option value="120">2 hours </option>

Internally the events are stored as StartTime/Duration, so this change did not effect the data.

When showing the event I look for a duration of 1440 and display "All Day" instead of the time.

A zero duration event is just a note or comment in the calendar. The note appears at the start time but duration is not shown.

The other values in the dropdown box are auto-generated based on the Calendar's "Time Interval" setting.

Dan

Sorry, I didn't made myself clear. I wasn't trying address all the problems of adding  "real" all day events.

I was only suggesting to the original poster that presenting the 24 hour event duration choice as "All Day" may be a way for them to add an "All Day" option without making a ton of changes to the code.

The above "All Day" event will just be a normal event lasting 1440 minutes unless they change the various calendars to display it differently.  This method is also very ugly if your users span multiple time zones.

Questions and comments welcome.

Dan