we have just migrated few users' mailboxes from Exchange 2010 to ZCS 8.0.6. Among other issues we have just found out that all users' allday events are shifted one day backwards. So for example if there is an allday event on 20.1.2014 on Exchange, after the migration it is on 19.1.2014 on ZCS.

Why is this happening. I can only guess that there is an misunderstanding between Exchange and Zimbra time format so for example 00:00 is taken as 24:00 or something like that.

On both Exchange and ZCS we have set time zone GMT+1.

Thanks for any clue.