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Try removing any all-day events from the calendar for the 1st April 2013 e.g. if you are syncing the calendar from somewhere else (e.g. Outlook on a PC or iCal/Calendar on a Mac) then change it to a timed event instead of all-day (if you don't sync your calendar from anywhere then try going into list view, go to 1st April and change any 'all day' events to times e.g. change Easter Monday to start at something like 4am) - it seems that there is a problem with all day events on that date which is when the clocks change due to daylight saving on the day before.
Acknowledgement: King Penguin.