[Javascript/HTML] Custom Timer

<html>
<?
    if ($_SERVER[PHP_SELF] != "/customtimer.php") {
        echo "<script>window.location.replace('http://sevens.pe.kr/customtimer.php'); </script>";
    }
    include_once("menu.php");
?>
<head>
<title>Seven's Timer - 커스텀 타이머</title>
<meta charset="utf-8">
</head>
<body>
<center>
<h2>커스텀 타이머</h2>
<br>
<br>
<form name="timer">
<input type="text" id="year" placeholder="년" maxlength="4"> <br>
<input type="text" id="month" placeholder="월" maxlength="2"> <br>
<input type="text" id="day" placeholder="일" maxlength="2"> <br>
<br>
<input type="button" name="ok" value="시작" onclick="countdowns();">
<br>
<br>
<div id="clock"></div>
</form>
<br>
<br>
<br>
해당 타이머는 테스트버전입니다. 불안정할 수 있습니다.
<br/>
<br/>
<br/>
<br/>
<h5>Hosting Provide By <a a href="http://storynetworks.kr" target="_blank">StoryNetworks</a></h5>
</body>
</center>
</html>
<script type="text/javascript" src="./js/countdown.timer.js">
        function countdowns()
        {
            var years = timer.year.value;
            var months = timer.month.value;
            var days = timer.day.value;
            var divid = "clock";
            if(years == "" || months == "" || days == "")
            {
                if(months == "1" || "2" || "3" || "4" || "5" || "6" || "7" || "8" || "9")
                {
                    countdown(years,months,"0".days,divid);
                }
                else
                {
                    countdown(years,months,days,divid);
                }
            }
            else
            {
                divid.innerHTML = "전부 입력해주세요.";
            }
            return;
        }
</script>