// JavaScript Document
function show_time(){
	Hours=document.getElementById("t4").value;
		if (Number(Hours)>=21){
			
		 	document.getElementById("t4d").value=(Number(Hours)-21)+":00";	
		}
		else
		{
			document.getElementById("t4d").value=(Number(document.getElementById("t4").value)+3)+":00";
			}

}