// en el template.php
 
function phptemplate_event_calendar_month($op, $header, $rows, $attributes = array(), $caption = NULL) {
  $attributes['summary'] = 'Calendar';  
  $output = theme("table", $header, $rows, $attributes, $caption);
  return '<div class="event-calendar"><div class="month-view">'. $output ."</div></div>\n";
}