def rfc1123_from_utc(dt):
    """
    Return a string representation of a date according to RFC 1123 (HTTP/1.1).
    The supplied date must be in UTC.

    """
    weekday = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"][dt.weekday()]
    month = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep",
             "Oct", "Nov", "Dec"][dt.month - 1]
    return "%s, %02d %s %04d %02d:%02d:%02d GMT" % (weekday, dt.day, month,
                                                    dt.year, dt.hour, dt.minute, dt.second)