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format javascript date in ISO 8601

There is a solution in StackOverflow:

/* use a function for the exact format desired... */
function ISODateString(d){
 function pad(n){return n<10 ? '0'+n : n}
 return d.getUTCFullYear()+'-'
      + pad(d.getUTCMonth()+1)+'-'
      + pad(d.getUTCDate())+'T'
      + pad(d.getUTCHours())+':'
      + pad(d.getUTCMinutes())+':'
      + pad(d.getUTCSeconds())+'Z'}

var d = new Date();
print(ISODateString(d)); // prints something like 2009-09-28T19:03:12Z

But there is already a function for this: toISOString, it came with ecmascript 5. Unfortunately, not all browsers support this, to solve this problem, we can provide our own prototype function for Date if it doesn’t exist:

if (!Date.prototype.toISOString) {
    Date.prototype.toISOString = function() {
        function pad(n) { return n < 10 ? '0' + n : n }
        return this.getUTCFullYear() + '-'
            + pad(this.getUTCMonth() + 1) + '-'
                + pad(this.getUTCDate()) + 'T'
                    + pad(this.getUTCHours()) + ':'
                        + pad(this.getUTCMinutes()) + ':'
                            + pad(this.getUTCSeconds()) + 'Z';

By the way, if you want to create an ISO string of DateTime in C#, use ToString(“s”):

var today = DateTime.Today;
var monthAgo = today.AddDays(-30);
var t = monthAgo.ToString("s");

Another way to convert a javascript date to ISO is to use JSON.stringify. The difference is that you get the date in ISO format surrounded with quotation marks. The curious thing is that Sys.Serialization.JavaScriptSerializer.serialize should do the same, but it returns the date in different format:

So it is the same date. Actually there is a deserialize function, too:


But why does the date look like “”\/Date(1326234740861)\/””. But when we get objects from an ajax call, we just get: “/Date(1326234740861)/”. The explanation must be in the deserialization inside $.ajax.

Parse Dates From ISO 8601

What if you want to create a date from iso in javascript. It is no problem if you use modern browsers:

var date = new Date(isoString);

But not in IE. Here it fails. So we have to create custom parsing functions for that. D-oh. (One solution could be to use moment.js):

Date.fromISOString = function (iso) {
    ///<summary>Is used to parse iso 8601 dates in IE
    ///partly inspired from
    var date = new Date(iso);
    if (isNaN(date)) {
        var minutesOffset = 0, numericKeys = [1, 4, 5, 6, 7, 10, 11];
        var struct = /^(\d{4}|[+\-]\d{6})(?:-(\d{2})(?:-(\d{2}))?)?(?:T(\d{2}):(\d{2})(?::(\d{2})(?:\.(\d{3}))?)?(?:(Z)|([+\-])(\d{2})(?::(\d{2}))?)?)?$/ .exec(iso);
        // avoid NaN timestamps caused by “undefined” values being passed to Date.UTC
        for (var i = 0, k; (k = numericKeys[i]); ++i) {
            struct[k] = +struct[k] || 0;

        // allow undefined days and months
        struct[2] = (+struct[2] || 1) - 1;
        struct[3] = +struct[3] || 1;

        if (struct[8] !== 'Z' && struct[9] !== undefined) {
            minutesOffset = struct[10] * 60 + struct[11];

            if (struct[9] === '+') {
                minutesOffset = 0 - minutesOffset;
        var s = Date.UTC(struct[1], struct[2], struct[3], struct[4], struct[5] + minutesOffset, struct[6], struct[7]);
        date = new Date(s);
    return date;

2 responses to “format javascript date in ISO 8601

  1. joarobles 2012-12-27 at 14:45

    excellent! i was looking for this functionality for the Date() object and finally used the ISODateString() you provide

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