When you’ve configured your Outlook.com account as an Exchange ActiveSync (EAS) account
in Outlook 2013, you indeed cannot delete any Calendars or Tasks folders from within Outlook. You’ll have to do that via the Calendar module of Outlook.com.
Note: When you’ve configured the Outlook.com account in Outlook 2003, 2007 or 2010 with the Outlook Hotmail Connector, you should be able to delete it by right clicking on it and choosing Delete but you can of course also do it via the Outlook.com website.
Manage Calendars on Outlook.com
You can access your Outlook.com Calendars by going to: Sign in to Calendar.Live.com