Question

Is there a string format of a date that a Date object can be built from (i.e. new Date('date string')) that works in all browsers and localities/timezones?

We’ve tried using the format suggested in the HTML5 spec of yyyy-mm-ddThh:mm:ss+hh:mm, but ran into issues with Safari and IE. We’ve tried using the less-formal format of mm/dd/yyyy hh:ss:mm which works but, as far as I know, “month before day” formatting can be ambiguous if your locale settings assume the first number to be a day (non-American countries). Also, it doesn’t attach a timezone which would have issues with different timezones.

Answer 1

In short that’s an almost impossible promise to make as the implementation is UA dependent. I would recommend using the iso8601 format as it will be standard going forward and use a shim to aid in the date parsing here is one I wrote for my own use:

(function() {

var d = window.Date,
    regexIso8601 = /^(\d{4}|\+\d{6})(?:-(\d{2})(?:-(\d{2})(?:T(\d{2}):(\d{2}):(\d{2})\.(\d{1,3})(?:Z|([\-+])(\d{2}):(\d{2}))?)?)?)?$/;

if (d.parse('2011-11-29T15:52:30.5') !== 1322581950500 ||
    d.parse('2011-11-29T15:52:30.52') !== 1322581950520 ||
    d.parse('2011-11-29T15:52:18.867') !== 1322581938867 ||
    d.parse('2011-11-29T15:52:18.867Z') !== 1322581938867 ||
    d.parse('2011-11-29T15:52:18.867-03:30') !== 1322594538867 ||
    d.parse('2011-11-29') !== 1322524800000 ||
    d.parse('2011-11') !== 1320105600000 ||
    d.parse('2011') !== 1293840000000) {

    d.__parse = d.parse;

    d.parse = function(v) {

        var m = regexIso8601.exec(v);

        if (m) {
            return Date.UTC(
                m[1],
                (m[2] || 1) - 1,
                m[3] || 1,
                m[4] - (m[8] ? m[8] + m[9] : 0) || 0,
                m[5] - (m[8] ? m[8] + m[10] : 0) || 0,
                m[6] || 0,
                ((m[7] || 0) + '00').substr(0, 3)
            );
        }

        return d.__parse.apply(this, arguments);

    };
}

d.__fromString = d.fromString;

d.fromString = function(v) {

    if (!d.__fromString || regexIso8601.test(v)) {
        return new d(d.parse(v));
    }

    return d.__fromString.apply(this, arguments);
};

})();

Now instead use Date.fromString(....) and everyone will be happy in the land of OZ!

works in all major browsers, used these references:

http://dev.w3.org/html5/spec/common-microsyntaxes.html

http://www.ecma-international.org/ecma-262/5.1/#sec-15.9.1.15

http://msdn.microsoft.com/en-us/library/windows/apps/ff743760(v=vs.94).aspx

http://msdn.microsoft.com/en-us/library/windows/apps/wz6stk2z(v=vs.94).aspx

http://msdn.microsoft.com/en-us/library/windows/apps/k4w173wk(v=vs.94).aspx

https://connect.microsoft.com/IE/feedback/details/723740/date-parse-and-new-date-fail-on-valid-formats

hope this helps -ck

UPDATE: (1/21/2013)

It should be noted that the behavior of what’s considered “standards-compliant behavior” is going to change from ECMAScript-262 v5.1 to ECMAScript-262 v6.0. See: http://people.mozilla.org/~jorendorff/es6-draft.html#sec-15.9.1.15

The language went from: The value of an absent time zone offset is “Z”. to If the time zone offset is absent, the date-time is interpreted as a local time.

The pickle right now is: chrome, opera and mobile safari follow ES5.1, whereas IE10, firefox and desktop safari seem to be following ES6. So it’s kind of a split decision right now… So as such there needs to be a second ES6 standard-compliant version of this script, and here ya go:

(function() {

    var d = window.Date,
        regexIso8601 = /^(\d{4}|\+\d{6})(?:-(\d{2})(?:-(\d{2})(?:T(\d{2}):(\d{2}):(\d{2})\.(\d{1,})(Z|([\-+])(\d{2}):(\d{2}))?)?)?)?$/,
        lOff, lHrs, lMin;

    if (d.parse('2011-11-29T15:52:30.5') !== 1322599950500 ||
        d.parse('2011-11-29T15:52:30.52') !== 1322599950520 ||
        d.parse('2011-11-29T15:52:18.867') !== 1322599938867 ||
        d.parse('2011-11-29T15:52:18.867Z') !== 1322581938867 ||
        d.parse('2011-11-29T15:52:18.867-03:30') !== 1322594538867 ||
        d.parse('2011-11-29') !== 1322524800000 ||
        d.parse('2011-11') !== 1320105600000 ||
        d.parse('2011') !== 1293840000000) {

        d.__parse = d.parse;

        lOff = -(new Date().getTimezoneOffset());
        lHrs = Math.floor(lOff / 60);
        lMin = lOff % 60;

        d.parse = function(v) {

            var m = regexIso8601.exec(v);

            if (m) {
                return Date.UTC(
                    m[1],
                    (m[2] || 1) - 1,
                    m[3] || 1,
                    m[4] - (m[8] ? m[9] ? m[9] + m[10] : 0 : lHrs) || 0,
                    m[5] - (m[8] ? m[9] ? m[9] + m[11] : 0 : lMin) || 0,
                    m[6] || 0,
                    ((m[7] || 0) + '00').substr(0, 3)
                );
            }

            return d.__parse.apply(this, arguments);

        };
    }

    d.__fromString = d.fromString;

    d.fromString = function(v) {

        if (!d.__fromString || regexIso8601.test(v)) {
            return new d(d.parse(v));
        }

        return d.__fromString.apply(this, arguments);
    };

})();