The "Date format" selection entry in the "Board Settings" is supposed to display its options according to the board's time zone. It does not however because there is a small coding oversight:

OPEN includes/acp/acp_board.php

FIND

		$user->timezone = $config['board_timezone'];

		$user->dst = $config['board_dst'];

REPLACE WITH

		$user->timezone = $config['board_timezone'] * 3600;

		$user->dst = $config['board_dst'] * 3600;