Calendar.setup = function (params) {
  function param_default(pname, def) { if (typeof params[pname] == "undefined") { params[pname] = def; } };

  param_default("inputField",     null);
  param_default("displayArea",    null);
  param_default("button",         null);
  param_default("eventName",      "click");
  param_default("ifFormat",       "%Y/%m/%d");
  param_default("daFormat",       "%Y/%m/%d");
  param_default("singleClick",    true);
  param_default("disableFunc",    null);
  param_default("dateStatusFunc", params["disableFunc"]);  // takes precedence if both are defined
  param_default("firstDay",       0); // defaults to "Sunday" first
  param_default("align",          "Br");
  param_default("range",          [1900, 2999]);
  param_default("weekNumbers",    true);
  param_default("flat",           null);
  param_default("flatCallback",   null);
  param_default("onSelect",       null);
  param_default("onClose",        null);
  param_default("onUpdate",       null);
  param_default("date",           null);
  param_default("showsTime",      false);
  param_default("timeFormat",     "24");
  param_default("electric",       true);
  param_default("step",           2);
  param_default("position",       null);
  param_default("cache",          false);
  param_default("showOthers",     false);

  var tmp = ["inputField", "displayArea", "button"];
  for (var i in tmp) {
    if (typeof params[tmp[i]] == "string") {
      params[tmp[i]] = document.getElementById(params[tmp[i]]);
    }
  }
  if (!(params.flat || params.inputField || params.displayArea || params.button)) {
    alert("Calendar.setup:\n  Nothing to setup (no fields found).  Please check your code");
    return false;
  }

  function onSelect(cal) {
    var p = cal.params;
    var update = (cal.dateClicked || p.electric);
    if (update && p.flat) {
      if (typeof p.flatCallback == "function")
        p.flatCallback(cal);
      else
        alert("No flatCallback given -- doing nothing.");
      return false;
    }
    if (update && p.inputField) {
      p.inputField.value = cal.date.print(p.ifFormat);
      if (typeof p.inputField.onchange == "function")
        p.inputField.onchange();
    }
    if (update && p.displayArea)
      p.displayArea.innerHTML = cal.date.print(p.daFormat);
    if (update && p.singleClick && cal.dateClicked)
      cal.callCloseHandler();
    if (update && typeof p.onUpdate == "function")
      p.onUpdate(cal);
  };

  if (params.flat != null) {
    if (typeof params.flat == "string")
      params.flat = document.getElementById(params.flat);
    if (!params.flat) {
      alert("Calendar.setup:\n  Flat specified but can't find parent.");
      return false;
    }
    var cal = new Calendar(params.firstDay, params.date, params.onSelect || onSelect);
    cal.showsTime = params.showsTime;
    cal.time24 = (params.timeFormat == "24");
    cal.params = params;
    cal.weekNumbers = params.weekNumbers;
    cal.setRange(params.range[0], params.range[1]);
    cal.setDateStatusHandler(params.dateStatusFunc);
    cal.create(params.flat);
    cal.show();
    return false;
  }

  var triggerEl = params.button || params.displayArea || params.inputField;
  triggerEl["on" + params.eventName] = function() {
    var dateEl = params.inputField || params.displayArea;
    var dateFmt = params.inputField ? params.ifFormat : params.daFormat;
    var mustCreate = false;
    var cal = window.calendar;
    if (!(cal && params.cache)) {
      window.calendar = cal = new Calendar(params.firstDay,
                   params.date,
                   params.onSelect || onSelect,
                   params.onClose || function(cal) { cal.hide(); });
      cal.showsTime = params.showsTime;
      cal.time24 = (params.timeFormat == "24");
      cal.weekNumbers = params.weekNumbers;
      mustCreate = true;
    } else {
      if (params.date)
        cal.setDate(params.date);
      cal.hide();
    }
    cal.showsOtherMonths = params.showOthers;
    cal.yearStep = params.step;
    cal.setRange(params.range[0], params.range[1]);
    cal.params = params;
    cal.setDateStatusHandler(params.dateStatusFunc);
    cal.setDateFormat(dateFmt);
    if (mustCreate)
      cal.create();
    cal.parseDate(dateEl.value || dateEl.innerHTML);
    cal.refresh();
    if (!params.position)
      cal.showAtElement(params.button || params.displayArea || params.inputField, params.align);
    else
      cal.showAt(params.position[0], params.position[1]);
    return false;
  };
};