var birthDate = new Date(1981, 1, 14); /* 2/14/81 (month is 0-based, yeesh) */
var today = new Date();
var age = today.getFullYear() - birthDate.getFullYear();
if (birthDate.getMonth() > today.getMonth() ||
    (birthDate.getMonth() == today.getMonth() && birthDate.getDate() > today.getDate())) {
  age -= 1; /* not yet to my birthday this year */
}
document.write(" <span title=\"age kept up-to-date via JavaScript 8-)\">I'm " + age + ", </span>");