When you change the NSTimeFormatString, iPhoto displays the creation times of photos in the same form.
Unfortunately, iPhoto also displays the date on its own, and the little text area is too small to display the date twice and then the time.
I suspect there are other apps that take a hit from this hack.

I'll have to try hacking Clock.menu.

I modified my time string to be: <%A / %b. %e / %1I:%M:%S%p> It works very well, with the exception that it causes some oddities to appear in the Watson T.V. Listings window, in the way that date is shown. These oddities appear to be purely cosmetic, however. They do not appear to cause any anomalous function. Probably affects iPhoto, too. I am not using iPhoto.

This problem is worse than cosmetic. When you try to edit a date in iPhoto it thinks you are still using the old format and gets thoroughly confused, so you end up with really strange dates.