How can i display time minus 6 hours

This is not a WordPress question, but to help you out:

function displaydate() {
    return date( 'd/m/Y G:i', strtotime( '-6 hours' ) );
}
add_shortcode('date', 'displaydate');

The shortcode itself should work fine.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)