I have not been able to figure out a way to remove that default alert of one day events in iCal? Is there any way of doing it? I use quite a bit of full day events as remainders of things, and I hate that I always have to go and manually remove the alert of each event.
Go to Calendar preferences and select alerts. Select None on All Day Events like in the image below. You have to do it for every Account defined (iCloud in the example image, but can be Gmail, On my Mac, Whatever...).