def get_timestamp(d):
    """
    Returns a UTC timestamp for a C{datetime.datetime} object.

    @type d: C{datetime.datetime}
    @return: UTC timestamp.
    @rtype: C{float}
    @see: Inspiration taken from the U{Intertwingly blog
        <http://intertwingly.net/blog/2007/09/02/Dealing-With-Dates>}.
    """
    if isinstance(d, datetime.date) and not isinstance(d, datetime.datetime):
        d = datetime.datetime.combine(d, datetime.time(0, 0, 0, 0))

    msec = str(d.microsecond).rjust(6).replace(' ', '0')

    return float('%s.%s' % (calendar.timegm(d.utctimetuple()), msec))