function checkDate(gg,mm,aaaa) 
  {
     err = 0

     if (mm<1 || mm>12) err = 1

     if (gg<1 || gg>31) err = 1
	
     if (isNaN(aaaa) || aaaa.length != 4) err = 1
	
     // months with 30 days
     if (mm==4 || mm==6 || mm==9 || mm==11){
        if (gg==31) err=1
     }

     // february
     if (mm==2){
     
       var g=parseInt(aaaa/4)
       if (isNaN(g)) {
		    err=1
       }

       if (gg>29) err=1
       if (gg==29 && ((aaaa/4) != parseInt(aaaa/4))) err=1
       if (gg==29 && ((aaaa/100) == parseInt(aaaa/100)) && ((aaaa/400) != parseInt(aaaa/400))) err=1
     }
     
     if(gg==1 && mm==1 && aaaa==1900) err = 1
     
     return err 

  }