I wondered if someone could help me with this. Just recently when I enter a new item into Calendar on Mavericks and wait a second it syncs and is fine on the iPhone and iPad and on iCloud website as a day timed event. When I then click to edit and enter the details and select all day event it spans that day and the following day only on the iPhone and iPad not on iCloud website nor on my Macbook Retina. I have read about adjusting Time Zone support and have tried numerous settings on all devices including setting all the same and also 'Off' and different combinations of these and makes no change at all, someone also mentioned about Daylight saving effected this but I can find no way of adjusting that or checking it. I hope somebody can help me with this as I am lost!!! Thanks in advance.