You'll need to have an action that is tied to your appointments object (mine is called Change Appointments) which you should get when you set Change to be a schedulable object. Once you have that action, you can put it into your workflow and I used copy rules to copy over the start and end date and used value types on the action to transfer over items like Title, Details etc...
Then you just need to define your calendar gadget in the web and apply your query (like All Changes).
<--- Start Date and End Date are done using Copy Rules on Change Appointments