In Version 1.4 we have added an export to iCalendar format for our rental calendars in the admin.

There is a great script here: https://github.com/nwcell/ics.js that makes it easy to add ics export from fullcalendar, or whatever calendar system you are using. Here is some quick sample code:

<div id="calendar">&nbsp;</div>
<script><br />
// First include jquery, fullcalendar, and ics.js and ics dependencies file from their github
// JSON calendar event sample
$eventsJSON = [ {
title: 'Event Title Sample',
start: '2015-07-22',
end: '2015-07-22',
description: 'description of calendar event'
}];
// basic fullcalendar code
$('#calendar').fullCalendar({
defaultDate: new Date(y, m, d),
editable: false,
events: $eventsJSON
});
// setup ics
var cal = ics();
// go through each event from the json and add an event for it to ics
$.each($eventsJSON,function(i,$event){
cal.addEvent($event.title, $event.description, '', $event.start, $event.end);
});
// Download iCal button onclick listener
$("#icaldownload").on('click',function(){
cal.download('ical','.ics');
});
</script>
<button id="icaldownload" style="float: right; margin-bottom: 10px;">Download iCal</button>