Zoho calendar 's link to iCal is very unreliable if recurring events are altered. We use calendar for weekly lessons in a school. If a lesson is cancelled and we change one event in the recurring weekly events, often the altered or unaltered events appear in zoho calendar but do not translate to iCal so do not show up on our iPhones. If you edit an event, add a space or something then resave, it sometimes fixes the problem but it's worrying that events drop off the calendar on our iPhones.