gistfile1.js

var parsedate = function (str) {
    // parsedate: String -> Date or null
    //
    // Decodes the timestamps from the ihackernews api, it seems like
    // they're produced by the following proc from news.arc.
    // 
    // (def text-age (a)
    //  (tostring
    //    (if (>= a 1440) (pr (plural (trunc (/ a 1440)) "day")    " ago")
    //        (>= a   60) (pr (plural (trunc (/ a 60))   "hour")   " ago")
    //                    (pr (plural (trunc a)          "minute") " ago"))))
    var now, match, num, scale, diff, units;

    match = /([0-9]+) ((day)|(hour)|(minute))s? ago/.exec(str);

    if (match === null) {
        return null;
    }

    units = {
        minute: 60000,
        hour: 3600000,
        day: 86400000
    };

    num   = Number(match[1]);
    scale = units[ match[2] ];
    diff  = num * scale; 
    now   = Date.now();

    return new Date(now - diff);
};

I think this is my new favourite version