import re


def isiso8601(value):
    """
    Return whether or not given value is ISO 8601 date.
    If the value is ISO 8601 date, this function returns ``True``, otherwise ``False``.

    Examples::

        >>> isiso8601('2009-12T12:34')
        True

        >>> isiso8601('2009367')
        False

    :param value: string to validate ISO 8601 date
    """
    iso8601 = re.compile(r'^([+-]?\d{4}(?!\d{2}\b))((-?)((0[1-9]|1[0-2])(\3([12]\d|0[1-9]|3[01]))?|W([0-4]\d|5[0-2])(-?[1-7])?|(00[1-9]|0[1-9]\d|[12]\d{2}|3([0-5]\d|6[1-6])))([T\s]((([01]\d|2[0-3])((:?)[0-5]\d)?|24:?00)([.,]\d+(?!:))?)?(\17[0-5]\d([.,]\d+)?)?([zZ]|([+-])([01]\d|2[0-3]):?([0-5]\d)?)?)?)?$')
    return bool(iso8601.match(value))