why getting different times when creating unix timestamps and converting back to datetime in javascript code example

Example 1: unix time to date javascript

const unixTime = 1210981217;
const date = new Date(unixTime*1000);
console.log(date.toLocaleDateString("en-US"));
//expected: "5/16/2008"

Example 2: how to format unix timestamp javascript

var s = new Date(1504095567183).toLocaleDateString("en-US")
// expected output "8/30/2017"  
console.log(s);