Starting with version 1.6, Otto makes a calendar feed available of all the migrations that have performed on that server. You can see what happened and click the provided link to be taken to the Migration Results page on the Otto Server.
You can turn this feature on and off on the Configuration page. Please note. You'll need to be logged in to Otto on a publically available URL, when you turn the feature on, for it to generate the right link for you. The calendar feed will not work if you don't do that.
No Events Yet Error
If you haven't done any migrations yet, there is nothing to put in the Calendar. This can cause some Calendar programs to throw an error when trying to subscribe. So if you get an error when you try to subscribe, please make sure you have done some migrations.