When changing time zone (i.e. - going one timezone east from Mountain time to Central time) all of the all-day events on the calendar are broken up into 2 days going from 11PM one day to 11PM the next day.
This works as designed. By default, VCO Calendar displays events using the event time zone. It displays the actual time of the events based on the original time zone of the events. So, when you move to different time zone, the start/end time of the events will be shifted to reflect the original time.
In VCO -> Calendar -> Settings, there is an option called "Lock Time Zone". You can enable this option if you want to keep the times and dates of the events even if you move to another time zone.