var startDate=new Date();
startDate.setFullYear(2012,00,9);// month - 1, input the day you want it live.
var endDate=new Date();
endDate.setFullYear(2012,00,22);// month - 1. input the day you want to kill it.
var today = new Date();

if (today >= startDate && today < endDate) 
  {
  document.write('<div id="banner"><img src="/images/banner/banner_1-12.jpg" alt="Winter Sidewalk Sale January 16-21" /><\/div>');
  }
else
  {
  }