Converting a .NET DateTime to a Javascript Date

Question

I have a WCF service that serves some dates to my javascript. I want to manipulate the date, but it arrives in the javascript looking like this:

/Date(1361145600000+0000)/

I know this is the miliseconds since 1970/01/01, but I havent been able to figure out how to convert it to a javascript Date.

Do I need to use a regex or trim the text to extract the miliseconds, and then use it like this:

new Date(miliseconds)

Surely there must be an easier way?

Answer 1

If the '+0000' is a standard timezone offset, the first 2 digits are hours, the last two, minutes.

Presumably it is not always '0000'-

You need to add(or subtract) the milliseconds difference from UTC to the first integral part to return the correct Date.

   function timeconvert(ds){
        var D, dtime, T, tz, off,
        dobj= ds.match(/(\d+)|([+-])|(\d{4})/g);
        T= parseInt(dobj[0]);
        tz= dobj[1];
        off= dobj[2];
        if(off){
            off= (parseInt(off.substring(0, 2), 10)*3600000)+
(parseInt(off.substring(2), 10)*60000);
            if(tz== '-') off*= -1;
        }
        else off= 0;
        return new Date(T+= off).toUTCString();
    }
    timeconvert('Date(1361145600000)+0000');

//returned value: (String UTC)

Mon, 18 Feb 2013 00:00:00 GMT

If the Dates ARE always in UTC ('+0000') you can just pull the significant digits from the string-

    function timeconvert(ds){
        var d=ds.match(/(\d+)/)[1];
        return new Date(+d).toUTCString();
    }
    timeconvert('Date(1361145600000)+0000)');

// returned value: (String UTC)

Mon, 18 Feb 2013 00:00:00 GMT

Answer 2

Code proposed by kennebec has a bug with a dates, that lower than 1 January 1970. For example, Date(-124054000000+0300) is Wed Jan 26 1966 07:33:20

Fixed code : http://output.jsbin.com/cejolu/3/edit?js,console

function timeconvert(ds){
    var D, dtime, T, tz, off,
        dobj = ds.match(/(-?\d+)|([+-])|(\d{4})/g);

    T = parseInt(dobj[0], 10);
    tz = dobj[1];
    off = dobj[2];

    if (off) {
        off = (parseInt(off.substring(0, 2), 10) * 3600000) + (parseInt(off.substring(2), 10) * 60000);
        if(tz == '-') off *= -1;
    }
    else off= 0;
    return new Date(T += off).toUTCString();
}

Test for the newest changes :

console.log(timeconvert("Date(-124054000000+0300)"));
console.log(timeconvert('Date(1361145600000)+0000'));
console.log(timeconvert("Date(0+0300)"));
console.log(timeconvert("Date(-2+0200)"));
console.log(timeconvert("Date(-860000000000+1100)"));

/* Output */

"Wed, 26 Jan 1966 07:33:20 GMT"
"Mon, 18 Feb 2013 00:00:00 GMT"
"Thu, 01 Jan 1970 03:00:00 GMT"
"Thu, 01 Jan 1970 01:59:59 GMT"
"Thu, 01 Oct 1942 18:06:40 GMT"