When I add a new item to my calendar, it saves, but doesn't show on the calendar.

I can add new items to my calendar and create alerts for them; however, whenever I go to the Calendar app and look for items I have created, they never show up. The only way I know the calendar is actually saving the items is because I get alerts when I have them set for and the items are syncing to my Outlook calendar (so I can see them on Outlook), but if I am looking for items on my phone Calendar app, they don't show. This was not a problem until about a month ago. I have shut down and reset the phone several times since the issue has started, but it is still not resolved.