Edit: The solution below does not work for iOS8. I will update if that gets fixed. For the moment, I’d recommend using a calendar app like Sunrise for this.
Last night, I was lamented with a friend about the different calendars we we keep and how it makes figuring out what we’re doing more complicated. To be specific, we were referring to our Facebook calendars and our Personal calendars. “If only,” we said, “there was a way to sync our events from facebook with our iphone calendars”. Of course, this is possible, but both of us had turned this option off, because it meant that our iphone calendars became cluttered with events that we had not yet accepted or had declined.
There had to be a solution to this, so I started digging.
The problem of events that have not been accepted or declined is a problem that requires that you either accept, decline or remove the events from facebook. This might take a bit of work at first, if you, like me, are one of those people who seems to leave a lot of events pending  (it actually didn’t take me as long as I thought it would to get through the pending events – maybe 5 minutes at most). However, once the initial work is done, you just have to keep up with new events.
But what about the declined events showing?  Most of the instructions I found online put this squarely on the shoulders of facebook, and instructed users to edit their facebook settings to hide declined events. This works fine in facebook (all declined events no longer show), but in IOS7, this does not seem to have any effect on the calendar app, which still shows all my declined events.
So, here’s how you fix this:
In the IOS calendar, at the bottom of the screen, Â click “calendars”.
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Scroll to the bottom of the following screen, and toggle “show declined events” to off.
Once done, your declined events will be gone from your iphone calendar.