currentyear.js

ar birthdate = new Date(1970, 1, 1);
var today = new Date();
var dayMs = 1000*60*60*24;
var startAge = 10;

var startPoint = new Date(birthdate.getTime());
startPoint.setYear(birthdate.getFullYear() + startAge);
var accum = startPoint.getTime();

for (var i = startAge; i < 100; i ++) {
  accum += dayMs*365*i / startAge;
  console.log(i, new Date(accum), (today.getTime() - accum) / dayMs);
}