This problem was encountered on phpBB.com's implementation of Olympus, in both the official community and the Area51 development board.

In the User Control Panel, I tried to set the "My date format" (Forum preferences > Edit global settings) to "r", to get an RFC 2822-formatted date. As a result, I got thrown a "TOO_SHORT_DATEFORMAT" error.

Is there a reason for setting the minimum number of characters that can be submitted into the field, or is it just something unintentional?