code: def calculate_leapdays(init_date, final_date):
      
  
      leap_days = (final_date.year - 1) // 4 - (init_date.year - 1) // 4
      leap_days -= (final_date.year - 1) // 100 - (init_date.year - 1) // 100
      leap_days += (final_date.year - 1) // 400 - (init_date.year - 1) // 400
  
      # TODO: Internal date correction (e.g. init_date is 1-March or later)
  
      return datetime.timedelta(days=leap_days)
docs: Currently unsupported, it only works for differences in years.