merci_pricing do not manage format date

If you use a non standard format that the strtotime function is capable to convert into timestamp, the total hours is zero and your prices are updated to zero.

in file includes/menu.inc

    $items = explode(',', $_POST['items']);
    $dates = array(
      strtotime($_POST['date'][0] . ' ' . $_POST['time'][0]),
      strtotime($_POST['date'][1] . ' ' . $_POST['time'][1]),
    );

  }

  $hours = round(($dates[1] - $dates[0]) / 3600, 2);