It seems to me that the quoted function from bzr

def local_time_offset(t=None):
    """Return offset of local zone from GMT, either at present or at time t."""
    # python2.3 localtime() can't take None
    if t is None:
        t = time.time()

    if time.localtime(t).tm_isdst and time.daylight:
        return -time.altzone
    else:
        return -time.timezone

would be very helpful to add to the `time` module docs as an example.  I have to agree with the OP that the current state of the docs is not as clear as it could be.