Time zone problem

Hi,

I am having a problem syncing calendar entries between zoho and zimbra because of time zone issues. I live in Illinois and have set zoho's time zone to be (GMT -6:0) Central Daylight Time (America/Chicago). Zimbra's time zone is set to GMT-6:00 US/Canada Central. I have set up share/subscribe in both directions and the appointments show up on both calendars. However the times are not always correct. In particular when I enter an all-day appointment in zimbra it imports in zoho for the previous day. I have also seen two appointments imported for the same day, one being imported correctly and the other being an hour off. Is there a way to see the time zone associated with an appointment? Is this a known issue?

Thanks
Ian