JS dynamically add Select option by system time limit

Although it is a simple effect, or need to accumulate, record a bit;

After August 1, delete the last item and add a new level 2016

— —Level 2015Level 2014Level 2013Level 2012

After June 1, delete the last item and add a new level 2016

— —Level 2016Level 2015Level 2014Level 2013

Source:

 <select id= "Myselect1", 
 <option value= "" >--</OPTION> 
 <option value= "Level 2015" >201 Level 5 </option> 
 <option value= "Level 2014" >2014 level </option> 
 <option value= "Level 2013" >2013 level </ Option> 
 <option value= "Level 2012" >2012 </option> 
 </select><br><br> 
 
 <select id= "Myselect2", 
 <option value= "" >--</OPTION> 
 <option value= "Level 2015" >2015 level < ;/option> 
 <option value= "Level 2014" >2014 </option> 
 <option value= "Level 2013" >2013 level </option 
 <option value= "level 2012" >2012 level </option> 
 </select> 
 
 var time = new Date (); 
 
  var month=time.getmonth () +1; 
 
   var day=time.getday ();  

    if (month>5&&day>1) {
        var Objselect=document.getelementbyid ("Myselect2");
        ObjSelect.options.add (New Option ("Level 2016", "Level 2016"), 1);
        ObjSelect.options.remove (5);
    }
    if (month>7&&day>1) {
        var Objselect=document.getelementbyid ("Myselect1");
        ObjSelect.options.add (New Option ("Level 2016", "Level 2016"), 1);
        ObjSelect.options.remove (5);
    }

JS dynamically add Select option by system time limit