def calculate_age(born):
 today = date.today()
 try:
  birthday = born.replace(year=today.year)
 except ValueError:
# raised when birth date is February 29 
# and the current year is not a leap year
  birthday = born.replace(year=today.year, day=born.day-1)
 if birthday > today:
  return today.year - born.year - 1
 else:
  return today.year - born.year