I've just got a new Lumia 920. Had it all set up with a number of hotmail/outlook.com accounts all of which are linked. The calendar sync'd with the main "microsoft" account neatly transferring my calendar into my new phone.
I was using the calendar, adding and deleting a few things when I noticed that only the birthdays from my secondary account were appearing. I checked "settings" in the calendar itself and everything was ok. Looking in the "E-mail and accounts" section of the phone "settings" I noticed that my main account has syn E-mail and nothing else. There is no option to select anything else to syn and I can find a way of uninstalling this "Microsoft" account and reinstalling it. I tried adding the account (a hotmail account) again and just having two of the same account with one that would sunc calendar but I got the error code 86000206 which I presume is to do with the fact that I have already added that account.
Does anyone have any ideas? I really need my calendar.