How do I find out the date taken of a pic on the iPhone 4
I can check when and where the photos on my iPhone 3gs were taken in a free app called Koredoko. It even gives u a map of where they were taken.
It doesn't appear that you are actually able to find a date the photo was taken. What you can do is connect it to your computer and save it there and label it with a date. That's the only way I've been able to do it.
Sorry for the shameless self promotion, but I just released an app that solves this problem. It's called 'Photo Date' (completely free) and shows you the date any of your existing photos were taken.