function calculate_age(birth_day,birth_month,birth_year)
{
    today_date = new Date();
    today_year = today_date.getYear();
    today_month = today_date.getMonth();
    today_day = today_date.getDate();
    age = (today_year + 1900) - birth_year;
    if ( today_month < (birth_month - 1))
    {
      age--;
    }
    if (((birth_month - 1) == today_month) && (today_day < birth_day))
    { 
      age--;
    }
    if (age > 1900)
    {
    age -= 1900;
    }
  return age;
}