from datetime import datetime


def calculate_itinerary_days(start_date, end_date):
    """ Calculate num_days for itinerary data based on start and end dates."""

    date_format = "%Y-%M-%d"
    start = datetime.strptime(start_date, date_format)
    end = datetime.strptime(end_date, date_format)
    delta = end - start

    return delta.days