Event length changes overnight

This is happening with a shared calendar that is on Outlook 2013 for 2 different Macs, 3 iPhones and 2 iPads. When an event is added to the calendar (example 1pm-2pm appointment tomorrow) overnight the event changes to be 5 hours in length (9am-2pm) for the same day. This does not happen to all appointments, and is seemingly random. It doesn't seem to matter which device adds the event (has been seen with appointments added from the Mac, iPhone and iPads). The appointment doesn't always end or start at the same time, it just "grows" to be 5 hours. Sometimes the end time is the same, but other times it is an hour later or even earlier than originally scheduled. There seems to be no rhyme or reason to it. This is an Outlook for Office 365 calendar. Initially all devices were not totally up to date on OS, but even after updating all devices to newest OS the issue seems to persist (it did it again last night, updates were done Friday). Any ideas?