User-Configurable Time Displays

I'm glad to see that you are using the API format_date() function on line 713 of guestbook.module.

However, you pass "medium" as the second parameter by default. You do not allow the user to specify the date format (short, medium, or long) on the Guestbook settings page.

Would it be possible to add a "Date format" setting on the Guestbook settings page? It would probably take less than 10 lines of code, and you might as well take advantage of the power of the Drupal API. In fact, if you are too busy to do this but still interested in the feature, I could even write a patch.