[@robin-w Moderator 9 years ago]

suggest you try this in your functions file

add_filter ('bbp_convert_date', 'rew_convert_date', 10 , 3 ) ;

function rew_convert_date ($time, $d, $translate) {
$d = 'G' ;
$time = mysql2date( $d, $time, $translate );
return apply_filters( 'rew_convert_date', $time, $d, $translate );
}

may or may not work !