How to create calendar using Javascript

<script LANGUAGE="JavaScript">
//Code from Mistonline.in
<!-- Begin
monthnames = new Array(
"January",
"Februrary",
"March",
"April",
"May",
"June",
"July",
"August",
"September",
"October",
"November",
"Decemeber");
var linkcount=0;
function addlink(month, day, href) {
var entry = new Array(3);
entry[0] = month;
entry[1] = day;
entry[2] = href;
this[linkcount++] = entry;
}
Array.prototype.addlink = addlink;
linkdays = new Array();
monthdays = new Array(12);
monthdays[0]=31;
monthdays[1]=28;
monthdays[2]=31;
monthdays[3]=30;
monthdays[4]=31;
monthdays[5]=30;
monthdays[6]=31;
monthdays[7]=31;
monthdays[8]=30;
monthdays[9]=31;
monthdays[10]=30;
monthdays[11]=31;
todayDate=new Date();
thisday=todayDate.getDay();
thismonth=todayDate.getMonth();
thisdate=todayDate.getDate();
thisyear=todayDate.getYear();
thisyear = thisyear % 100;
thisyear = ((thisyear < 50) ? (2000 + thisyear) : (1900 + thisyear));
if (((thisyear % 4 == 0) 
&& !(thisyear % 100 == 0))
||(thisyear % 400 == 0)) monthdays[1]++;
startspaces=thisdate;
while (startspaces > 7) startspaces-=7;
startspaces = thisday - startspaces + 1;
if (startspaces < 0) startspaces+=7;
document.write("<center><table border=4 bgcolor=white ");
document.write("bordercolor=#000><font color=>");
document.write("<tr><td colspan=7><center><strong>" 
+ monthnames[thismonth] + " " + thisyear 
+ "</strong></center></td></tr></font>");
document.write("<tr>");
document.write("<td align=center>Su</td>");
document.write("<td align=center>M</td>");
document.write("<td align=center>Tu</td>");
document.write("<td align=center>W</td>");
document.write("<td align=center>Th</td>");
document.write("<td align=center>F</td>");
document.write("<td align=center>Sa</td>"); 
document.write("</tr>");
document.write("<tr>");
for (s=0;s<startspaces ;s++) {
document.write("<td> ");
}
count=1;
while (count <= monthdays[thismonth]) {
for (b = startspaces;b<7;b++) {
linktrue=false;
document.write("<td>");
for (c=0;c<linkdays .length;c++) {
if (linkdays[c] != null) {
if ((linkdays[c][0]==thismonth + 1) && (linkdays[c][1]==count)) {
document.write("<a href=\"" + linkdays[c][2] + "\">");
linktrue=true;
      }
   }
}
//code from Mistonline.in
if (count==thisdate) {
document.write("<font color=blue><strong>");
}
if (count <= monthdays[thismonth]) {
document.write(count);
}
else {
document.write(" ");
}
if (count==thisdate) {
document.write("</strong></strong></font>");
}
if (linktrue)
document.write("");
document.write("");
count++;
}
document.write("</linkdays></startspaces></tr>");
document.write("<tr>");
startspaces=0;
}document.write("");
document.write("</tr><tr>");
document.write("<td align=center></td>");
document.write("</tr>");</script>

<style>
table {
  border-collapse: collapse;
  width: 50%;
}

th, td {
  text-align: left;
  padding: 8px;
}

td:nth-child(even){background-color: #f2f2f2}
td:hover {background-color: #ddd;}
th {
  background-color: #04AA6D;
  color: white;
}
</style>

document.write("<td align=center>Su</td>");
document.write("<td align=center>M</td>");
document.write("<td align=center>Tu</td>");
document.write("<td align=center>W</td>");
document.write("<td align=center>Th</td>");
document.write("<td align=center>F</td>");
document.write("<td align=center>Sa</td>");