How can I convert a date value in UTC format to a date object in Javascript

var ISODate = {
    convert : function (input){
        if (!(typeof input === "string")) throw "ISODate, convert: input must be a string";
        var d = input.match(/^(d{4})-(d{2})-(d{2})[T ](d{2}):(d{2}):(d{2}(?:.d+)?)(Z|(([+-])(d{2}):(d{2})))$/i);
        if (!d) throw "ISODate, convert: Illegal format";
        return new Date(
            Date.UTC(d[1],d[2]-1,d[3],d[4],d[5],d[6]|0,(d[6]*1000-((d[6]|0)*1000))|0,d[7]) +
            (d[7].toUpperCase() ==="Z" ? 0 : (d[10]*3600 + d[11]*60) * (d[9]==="-" ? 1000 : -1000))
        );
    },
    format : function(t,utc){
        if (typeof t === "string") t = this.convert(t);
        if (!(t instanceof Date)) throw "ISODate, format: t is not a date object";
        t = utc ?
            [t.getUTCFullYear(),t.getUTCMonth(),t.getUTCDate(),t.getUTCHours(),t.getUTCMinutes(),t.getUTCSeconds()] :
            [t.getFullYear(),t.getMonth(),t.getDate(),t.getHours(),t.getMinutes(),t.getSeconds()];

        return this.month[t[1]] + " " +this.ordinal(t[2]) + ", " +t[0] +
            " @ " + this.clock12(t[3],t[4]);
    },
    month:["January","February","March","April","May","June","July","September","October","November","December"],
    ordinal:function(n) {
        return n+(["th","st","nd","rd"][(( n % 100 / 10) | 0) ===1 ? 0 : n % 10 < 4 ? n % 10 : 0 ]);
    },
    clock12:function(h24,m,s){
        h24%=24;
        var h12 = h24 % 12;
        if (h12===0) h12=12;
        return h12 + ":" +
            (m<10 ? "0" + m : m) +
            (isFinite(s) ? ":" + (s<10?"0"+s:s): "") +
            (h24<12 ? "AM":"PM");
    }
};

//Shows the date in the users timezone:
alert(ISODate.format("2007-09-21T14:15:34.058-07:00"));

//Show the date in UTC (Timezone Z, 00:00)
alert(ISODate.format("2007-09-21T14:15:34.058-07:00",true));