Runs through a folder and prepends all photo filenames with its taken date and time according to the Exif data. The heavy lifting is done by the exifr gem. This is just a hitch for it.
Need to add the execute bit permission:
$ chmod +x exifdater.rb
$ exifdater.rb path/to/photos
EXIF Reader. If you don't have the gem, install it.
gem install exifr