var age = new Date();
var day = age.getDate();
var year = age.getYear();
var month = (age.getMonth() + 1);
if (year < 1000) {
  year += 1900;
}

var my_day = 6; // Day of birth
var my_month = 5; // Month of birth
var my_year = 1975; // Year of birth
var my_msg = (year - my_year); // Message
var my_set = 0; // 1 = Enable the birthday message · 0 = Disable the birthday message

if ((day == my_day) && (month == my_month)) {
  my_age = year - my_year;
  if (my_set == 0) {
    my_msg = null;
    }
}
else if ((day >= my_day) && (month >= my_month)) {
  my_age = year - my_year;
}
else if ((day < my_day) && (month == my_month)) {
  my_age = --year - my_year;
}
else if ((day < my_day) && (month > my_month)) {
  my_age = year - my_year;
}
else {
  my_age = --year - my_year;
}
document.write (my_age);