def calc_runtime(start, end):
    """ Calculates job runtime given start, end datetime stamps
    Args:
        - start (datetime object): job start timestamp
        - end (datetime object): job end timestamp
    """
    duration = end - start
    if (duration.seconds / 60) < 1:
        return (duration.seconds), 'seconds'
    else:
        return (duration.seconds / 60), 'minutes'