As a photographer I want to sort the photos that I took by the date I took them, so I can easily find them afterwards.
To make that easier I got myself the nifty exiv2. Like so (if you got a mac and have homebrew installed):
brew install exiv2
Then you can easily rename your photos:
exiv2 -tr "%Y%m%d_:basename:" mv path_to_photos
Check the manpage of exiv2 for further infos.