Welcome to iMore! The time for an all day event does not show 9 am. It shows a date like, Thurs., Dec. 4, 2014. It does alert you to the all day event at 9 am or times before 9am. But if it's an all day event, why would you want to be alerted at 5:00 pm? You could turn off the all day event and set the alarm for 5:00 pm. Or, leave it All Day Event. Set a reminder for 5:00 pm in the Reminders app.