ValidateDate.js

//e.g. input 2016-10-18

function validateDateInputHelper(val) {
  if (!val) return true;
  var parts = val.split('-');

  if (parseInt(parts[0], 10) == 0 || parts[1] == '00' || parts[2] == '00') {
    return false;
  }

  var year = parseInt(parts[0], 10);
  var month = parseInt(parts[1], 10);
  var day = parseInt(parts[2], 10);

  if (year && year.length == 4 && year < 1000 || year > 3000 ) {
    return false;
  }

  if (month && month.length == 2 && month > 12) {
    return false;
  }

  if (day) {
    var monthLength = [ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 ];
    // Consider leap years
    if (year % 400 == 0 || (year % 100 != 0 && year % 4 == 0))
    {
      monthLength[1] = 29;
    }
    return day <= monthLength[month - 1];
  }

  return true;
}