Javascript 如何修改Mailchimp订户弹出（嵌入）cookie

默认过期时间为1年。我想要1周

嵌入代码就是这个

如何做到这一点

    if(document.cookie.indexOf("MCEvilPopupClosed") > 0 ){

    //check if (Cookie was created more than 7 days){delete cookie} 

    }