function dateChanged(calendar) {
    // Beware that this function is called even if the end-user only
    // changed the month/year.  In order to determine if a date was
    // clicked you can use the dateClicked property of the calendar:
    if (calendar.dateClicked) {
      // OK, a date was clicked, redirect to /yyyy/mm/dd/index.php
      var y = calendar.date.getFullYear();
      var m = calendar.date.getMonth() + 1;     // integer, 0..11
      var d = calendar.date.getDate();      // integer, 1..31
      // redirect...
      window.location =  "" + "archive.php?isuuedate=" + y + "-" + m + "-" + d;
    }
  };

  Calendar.setup(
    {
      inputField  : "data",         // ID of the input field
      ifFormat    : "%Y-%m-%d",    // the date format
      onSelect : dateChanged,           // our callback function
      firstDay : 0,
      weekNumbers : false,
      range : [2006, 2009]
    }
  );