日付を表示させるメモ

<script type="text/javascript">
mydate=new Date();
Ye=mydate.getFullYear();
Mo=mydate.getMonth()+1;
Da = mydate.getDate();
if(Da < 21) {
  document.write(Ye+"年"+Mo+"月");
}
if(Da > 20) {
  Mo=Mo+1;
  if(Mo < 13) {  
    document.write(Ye+"年"+Mo+"月");
  }
  if(Mo > 12) {
    Mo=Mo-12;
    Ye=Ye+1;
    document.write(Ye+"年"+Mo+"月");
  }
}
</script>