def METHOD_NAME(cls, date_str):
    if date_str is None:
        return None
    try:
        date_arr = date_str.split("/")
        if len(date_arr) > 1:
            start_dt = parser.parse(date_arr[0])
            end_dt = parser.parse(date_arr[1])
            return TimeIntervalFormat(start_dt, end_dt)
        else:
            single_dt = parser.parse(date_str)
            return TimeIntervalFormat(single_dt)
    except Exception:
        raise ValueError("Error parsing datetime string: %s" % date_str)