def now(tz=None):
    """Return the current local date and time.

        If optional argument tz is None or not specified, this is like today(),
        but, if possible, supplies more precision than can be gotten from going
        through a time.time() timestamp (for example, this may be possible on
        platforms supplying the C gettimeofday() function).

        Else tz must be an instance of a class tzinfo subclass, and the current
        date and time are converted to tz's time zone. In this case the result
        is equivalent to tz.fromutc(datetime.utcnow().replace(tzinfo=tz)).

        See also today(), utcnow().
        """
