from datetime import datetime


def _get_filename(from_date, to_date, time_format='%Y%m%dT%H%M%SZ'):
    """Generates filename (without file extension) as time interval."""
    from_date_str = datetime.strftime(from_date, time_format)
    to_date_str = datetime.strftime(to_date, time_format)
    return f'{from_date_str}--{to_date_str}'