Exchange calendar items show up a day later for multi-day events.

We just switched to MS Exchange Online and when we create a calendar meeting or appt in MS Outlook it shows up on the iphones and ipads as a day later, also shows up as an all-day event. Anyone know a fix for this? We have 5 iPhones 4 and 4s in the office on both AT&T and Verizon and all have the same issues.