This widget is an easy to use and completely integrated "Add to Calendar" button for your websites (this works for all wordpress and blogger hosted platforms). You can also integrate facebook Events in this widget.
Example:-
Follow these Steps to Add this Widget to Blogger or Any Site:-
Step 1: Copy and paste the following code between the <body> and the </body> tags.
<script type="text/javascript" src="http://js.addthisevent.com/atemay.js"></script>
Step 2: Copy and paste following code where you want widget to display (example:- Adding Calendar to posts or main menu links)
All link properties are not mandatory, however you need to provide a title of your event as well as dates.
<a href="http://example.com/link-to-your-event" title="Add to Calendar" class="addthisevent"> Add to Calendar <span class="_url">http://example.com/link-to-your-event</span> <span class="_start">10-05-2012 11:38:46</span> <span class="_end">11-05-2012 11:38:46</span> <span class="_summary">Summary of the event</span> <span class="_description">Description of the event</span> <span class="_location">Location of the event</span> <span class="_organizer">Organizer</span> <span class="_organizer_email">Organizer e-mail</span> <span class="_facebook_event">http://www.facebook.com/events/160427380695693</span> <span class="_all_day_event">true</span> <span class="_date_format">DD/MM/YYYY</span> </a>
Note:- HTTPS is not yet supported. However you can download this package for local usage and upload it to your own server
Source Website -AddThisEvent