anchor.diff:  		});
   		
     function zoom(incr) {
  -    var slider = $('#zoom_slider')
  -    slider.slider('value', slider.slider('option', 'value') + incr);
  -    update_calendar_zoom(slider.slider('option', 'value'));
  +    update_calendar_zoom($('#zoom_slider').slider('option', 'value') + incr);
     }		
     
     function update_calendar_zoom(value) {
  
positive.code:   }
    
    // set default zoom and scroll to today
    $('#zoom_slider').slider('option', 'value', '7');
    update_calendar_zoom(7);
  	
    var todayCol = $('td[data="<%= Date.today.strftime('%Y-%m-%d') %>"]');
    var scrollArea = $('#staff_calendar_scroll');
    if (todayCol) {
  
negative.code: 		$(".week_days").css('display', (value > 4 ? 'inline' : 'none'));
  		$(".days").css('display', (value > 6 ? 'inline' : 'none'));
  		
      $('#zoom_slider').slider('option', 'value', value);
  
  		var width, border;
  		
  		switch(value) {
  