How can I hide All-day events in the calendar on my i-phone 4?

If you have iCloud calendars set up on your iPhone, you should have several iCloud calendars. I have Calendar, Work, Home. When you create an all day even put it in one of the calendars. For instance, i would put it in the Calendar calendar. You can select the calendar when entering the event by tapping Calendar label. You can then hide the all day events by tapping the Calendars button located top left on screen (portrait mode), then tap the name of the calendar you used to uncheck. When click done, your all day events will be hidden. Note you will have to rehide the calendar after adding a new all day event.