This response is for iPad/iPhone: Go into Settings, then "Mail, Contacts, Calendars". Open the individual settings for each email account separately. Each account gives you the option of turning on or off calendars. For Gmail and Yahoo email accounts on your device (and presumably other email service providers) turn OFF the calendar. What is happening is that the calendar settings in your Gmail/Yahoo email accounts may be overriding your device settings, hiding all calendar data after 30 days. The data should still be there, so once you turn off the other email calendars in your device, your device calendar should repopulate with all past calendar events. My Mac never had this problem - just my mobile devices. Hope this helps some of you!