<html>
<head>
</head>
<body>
<div class="date">c-<input type="date">-по-<input type="date">-<span></span></div>
<script>
document.querySelector('.date').oninput=function(){
var inp = document.querySelectorAll('input[type="date"]'),
span = document.querySelector('.date>span'),
s = new Date(inp[0].value), po = new Date(inp[1].value);
if(s>=-1577923200000 && po<=-1511654400000 && s<po) span.textContent ='1%';
else if(s>=-1511654400000 && po<=-1450656000000 && s<po) span.textContent ='1.5%';
else span.textContent ='';
console.log(s);
}
</script>
</body>
</html>
