from datetime import datetime


def find_age_band(birth_date: str, end_date: datetime) -> str:
  """Given the birth date, finds the age_band for PEPFAR disaggregation."""
  birth = datetime.strptime(birth_date, '%Y-%m-%d')
  age = int((end_date - birth).days / 365.25)
  if age < 1:
    return '0-1'
  if age <= 4:
    return '1-4'
  if age <= 9:
    return '5-9'
  if age <= 14:
    return '10-14'
  if age <= 19:
    return '15-19'
  if age <= 24:
    return '20-24'
  if age <= 49:
    return '25-49'
  return '50+'