曜日です。
<HTML>
<HEAD>
<TITLE></TITLE>
<SCRIPT LANGUAGE="JavaScript">
weekday=new Array("日","月","火","水","木","金","土");
function day(){
     myDate = new Date();
     myDate.setFullYear(document.form1.year.value);
     myDate.setMonth(document.form1.month.value-1);
     myDate.setDate(document.form1.date.value);
     document.form1.week.value=weekday[myDate.getDay()];
}
</SCRIPT>
</HEAD>
<BODY>
<CENTER>
<FORM NAME="form1">
<INPUT TYPE="text" NAME="year" STYLE="ime-mode:disabled" SIZE="4"> 年
<INPUT TYPE="text" NAME="month" STYLE="ime-mode:disabled" SIZE="1"> 月
<INPUT TYPE="text" NAME="date" STYLE="ime-mode:disabled" SIZE="1"> 日
<INPUT TYPE="button" VALUE="CLICK" onClick="day()">
<INPUT TYPE="text" NAME="week" SIZE="1"> 曜日です。
<INPUT TYPE="reset" VALUE="CLEAR">
</FORM>
</CENTER>
</BODY>
</HTML>