Handler for when the DatePicker for a field fires the 'select' event
@param {Ext.picker.Date} picker
@param {Object} date
function (picker, date) {
        // NOTE: we need to redefine the picker.
        var me = this,
            menu = me.menu,
            checkItemId = menu.getFocusEl().itemId.replace(me.reItemId, '$1'),
            fields = me.fields,
            field;

        picker = menu.queryById(checkItemId);
        field = me.fields[picker.itemId];
        field.setChecked(true);

        if (field == fields.on) {
            fields.before.setChecked(false, true);
            fields.after.setChecked(false, true);
        } else {
            fields.on.setChecked(false, true);
            if (field == fields.after && me.getFieldValue('before') < date) {
                fields.before.setChecked(false, true);
            } else if (field == fields.before && me.getFieldValue('after') > date) {
                fields.after.setChecked(false, true);
            }   
        }   
        me.fireEvent('update', me);

        // The timepicker's getBubbleTarget() returns the boundlist's implementation,
        // so it doesn't look up ownerCt chain (it looks up this.pickerField).
        // This is a problem :)
        // This can be fixed by just walking up the ownerCt chain
        // (same thing, but confusing without comment).
        picker.ownerCt.ownerCt.hide();
    }