lastModified problems in Netscape 6

[reeset]

I've been using this script for a while without trouble, but I was redesigning my site, and decided to take a look at the layout with Netscape 6, since my logs are showing more users visiting with this browser. I was a bit suprised to see that my footer script, printing the date of the last file modification was showing up incorrectly. Can someone help. Here is the script:

<script language="JavaScript"><!--
function makeArray0() {
     for (i = 0; i<makeArray0.arguments.length; i++)
          this[i] = makeArray0.arguments[i];
}

var days = new makeArray0("Sunday","Monday","Tuesday","Wednesday",
    "Thursday","Friday","Saturday");

var months = new makeArray0('January','February','March',
    'April','May','June','July','August','September',
    'October','November','December');

function nths(day) {
     if (day == 1 || day == 21 || day == 31) return 'st';
     if (day == 2 || day == 22) return 'nd';
     if (day == 3 || day == 23) return 'rd';
     return 'th';
}

function getCorrectedYear(year) {
    year = year - 0;
    if (year < 70) return (2000 + year);
    if (year < 1900) return (1900 + year);
    return year;
}

function y2k(number) { return (number < 1000) ? number + 1900 : number; }

var last = document.lastModified;
var date = new Date(last);
var dateY2K = new Date(getCorrectedYear(date.getYear()),date.getMonth(),date.getDate());

document.write("Last updated on " + days[dateY2K.getDay()] + ' ' +
    dateY2K.getDate() + nths(dateY2K.getDate()) + " " +
    months[dateY2K.getMonth()] + ", " +
    (y2k(dateY2K.getYear())) + ".");
//--></script>

In Netscape 6, I get: Last updated on Tuesday 31st December, 2069.
In IE 4,5 and Netscape 4 I get: Last updated on Monday 6th August, 2001.

Thanks for the help.