- Control-click on iPhoto, click on "Show Package Contents" and locate Contents -> Resources -> English.lproj -> Localizable.strings
- Back this file up if you like, then double click on it. The file should open in text edit.
- Scroll down to just beyond 75% of the way down the page, and look for the heading // Date/time formatting.
- You should see beneath that DateShortFormat = "%m/%d/%y"; // Used for rolls
- To change the format into DD/MM/YY, simply change %m into %d and vice versa. The string should now read: DateShortFormat = "%d/%m/%y"; // Used for rolls
- To use another date format, visit this page at about.com which lists all the UNIX date and time commands which can be used in any combination you like. [robg adds: or type man strftime in the Terminal...
- Simply save the file and check to see if it works in iPhoto.
Warning: When editing strings, make sure you only edit text within quotation marks. Hope this helps someone!

