def timefstring(dtobj, tz_name=True):
    """Standardize the format used for timestamp string format.
    Include 3 letter string for timezone if set to True.
    """
    if tz_name:
        return f'{dtobj.strftime("%Y-%m-%d_%H:%M:%S%Z")}'
    else:
        return f'{dtobj.strftime("%Y-%m-%d_%H:%M:%S")}NTZ'