input: datetime
    output: float utc seconds since THIS DAY'S MIDNIGHT

def datetime2utsec(t: Union[str, datetime.date, datetime.datetime, np.datetime64]) -> float:
    """
    input: datetime
    output: float utc seconds since THIS DAY'S MIDNIGHT
    """
    if isinstance(t, (tuple, list, np.ndarray)):
        return np.asarray([datetime2utsec(T) for T in t])
    elif isinstance(t, datetime.date) and not isinstance(t, datetime.datetime):
        return 0.
    elif isinstance(t, np.datetime64):
        t = t.astype(datetime.datetime)
    elif isinstance(t, str):
        t = parse(t)

    return datetime.timedelta.total_seconds(t - datetime.datetime.combine(t.date(),
                                                                          datetime.datetime.min.time()))