How to get rid of Facebook birthday’s on my Calendar?

I've recently connected my facebook account with my Outlook. Then suddenly, I've got tons of birthday reminders at my Outlook account, and even more I can't delete some of them: it comes with a Calendar Error and with this statement "Sorry, there’s a problem deleting this birthday at the moment. Please try again later." I would like some suggestions from the community or from Microsoft of any possible ways to delete the birthdays that are now on my Outlook calendar. I've already switched off the birthday reminders, rather I want all of them gone. So any help out there? 

Thanks,

Bradley