From Facebook Developers Wiki

I think it would really increase the functionality of this element to have an argument that allows developers to choose the formatting for the time, similar to the PHP date() function. The <fb:time> element is really crucial to anything that requires time functionality because of the differences in timezones, and would remove the need to make an expensive API call.

Chad Fulton - 11511951 10:19, 21 December 2007 (PST)

I agree. It would be an incredible help if we could do some formatting. This tag renders some ugly times, but it's very useful to be able to display local times. This should happen soon. --683998405 08:06, 6 March 2008 (PST)