maxJSDate.js

module.exports = function findMaxValidDate(min, max) {
  var next = Math.floor((min+max)/2);

  if(min == next) return min;

  if(new Date(next) == "Invalid Date") {
    return findMaxValidDate(min, next);
  } else {
    return findMaxValidDate(next, max);
  }
}

console.log(module.exports(0, Number.MAX_VALUE));