function calendar() {
   calDate=new Date()
   
   document.write("<table id='calendar_table'>");
   writeCalTitle(calDate);
   writeDayNames();
   writeCalDays(calDate);
   document.write("</table>");
}

function writeCalTitle(calendarDay) {
   var monthName = new Array("January", "February", "March", "April", "May", 
   "June", "July", "August", "September", "October", "November", "December");

   var thisMonth=calendarDay.getMonth();
   var thisYear=calendarDay.getFullYear();

   document.write("<tr>");
   document.write("<th id='calendar_head' colspan='7'>");
   document.write(monthName[thisMonth]+" "+thisYear);
   document.write("</th>");
   document.write("</tr>");
}

function writeDayNames() {
   var dayName = new Array("Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat");
   document.write("<tr>");
   for (var i=0;i<dayName.length;i++) {
      document.write("<th class='calendar_weekdays'>"+dayName[i]+"</th>");
   }
   document.write("</tr>");
}

function daysInMonth(calendarDay) {
   var thisYear = calendarDay.getFullYear();
   var thisMonth = calendarDay.getMonth();
   var dayCount = new Array(31,28,31,30,31,30,31,31,30,31,30,31);
   if (thisYear % 4 == 0) {
      if ((thisYear % 100 !=0) || (thisYear % 400 == 0)) {
         dayCount[1] = 29; // this is a leap year
      }
   }
   return dayCount[thisMonth]; // return the number of days in the month
}

function writeCalDays(calendarDay) {
   var currentDay = calendarDay.getDate();

   // determine the starting day of the week
   var dayCount = 1;
   var totalDays = daysInMonth(calendarDay);
   calendarDay.setDate(1);              // set the date to the first day of the month
   var weekDay = calendarDay.getDay();  // the day of week of the first day

   // write blank cells preceding the starting day
   document.write("<tr>");
   for (var i=0; i < weekDay; i++) {
      document.write("<td></td>");
   }

   // write cells for each day of the month
   while (dayCount <= totalDays) {
      // write the table rows and cells
      if (weekDay == 0) document.write("<tr>");

      if (dayCount == currentDay) {
         // highlight the current day
         document.write("<td class='calendar_dates' id='calendar_today'>"+dayCount+"</td>");
      } else {
         // display the day as usual
         document.write("<td class='calendar_dates'>"+dayCount+"</td>");
      }

      if (weekDay == 6) document.write("</tr>");

      // move to the next day
      dayCount++;
      calendarDay.setDate(dayCount);
      weekDay = calendarDay.getDay();
   }
   document.write("</tr>");
}