Chrome believes ISO time that lacks Z is in UTC; problem with C#

Question

Chrome believes ISO time that lacks Z is in UTC; problem with C#

Check out this jsfiddle: http://jsfiddle.net/E9gq9/7/ on Chrome, Firefox, and Internet Explorer and see the differences:

Chrome:

Chrome http://images.devs-on.net/Image/vBTz86J0f4o8zlL3-Region.png

Firefox:

Firefox http://images.devs-on.net/Image/aNPxNPUpltyjVpSX-Region.png

IE:

IE http://images.devs-on.net/Image/WXLM5Ev1Viq4ecFq-Region.png

Safari:

Safari http://images.devs-on.net/Image/AEcyUouX04k2yIPo-Region.png

ISO 8601 does not provide clear guidelines on how to interpret a string without a trailing Z.

Our server (ASP.NET MVC4) is fetching UTC times from our database as DateTimes and directly passing them into JSON. This has caused inconsistencies across different browsers.

Should we consider adding a Z at the end of the timestamps on the server side before sending them to the client?

javascript asp.net datetime utc

Answer 1

Answer №1

Is it advisable to append Z to dates on the server side?

In summary Yes, it is recommended.

The correct handling of dates and date/times without a timezone has evolved over time, with variations in specifications and adherence by JavaScript engines.

Back in 2013 when this answer was first written, the ES5 spec stated that no timezone meant UTC:

The value of an absent time zone offset is “Z”.

However, this conflicted with ISO-8601 where the absence of a timezone indicator indicated local time. Some implementations stuck with ISO-8601 instead of ES5's definition.

In ES2015 (ES6), the specification was changed to align with ISO-8601:

If the time zone offset is absent, the date-time is interpreted as a local time.

Nevertheless, this change led to compatibility issues, especially with date-only formats like 2018-07-01. Subsequently, in ES2016, the interpretation was adjusted again:

When the time zone offset is absent, date-only forms are interpreted as UTC time and date-time forms are interpreted as local time.

For example, new Date("2018-07-01") is parsed as UTC, while new Date("2018-07-01T00") is parsed as local time.

These rules have remained consistent in ES2017 and upcoming ES2018 versions; you can refer to the current editor's draft for more details.

You can test your browser's behavior using the provided code snippet.

Current browser support status as of September 2021:

Modern Firefox, Chrome, and Safari browsers handle this correctly, including iOS browsers.
Interestingly, IE11 also interprets dates accurately.

Past browser support status as of April 2018:

IE11 handled dates correctly.
Firefox had accurate date interpretations.
Chrome 65 got it right on desktop and Android platforms.
However, there were issues with Chrome 64 (iOS) and iOS Safari in parsing date/time forms incorrectly as UTC.

An open issue related to date parsing in V8 engine from Chrome 64 to 65 has been resolved, but specific details are not readily available.

Answer 2

Is it advisable to append Z to dates on the server side?

In summary Yes, it is recommended.

The correct handling of dates and date/times without a timezone has evolved over time, with variations in specifications and adherence by JavaScript engines.

Back in 2013 when this answer was first written, the ES5 spec stated that no timezone meant UTC:

The value of an absent time zone offset is “Z”.

However, this conflicted with ISO-8601 where the absence of a timezone indicator indicated local time. Some implementations stuck with ISO-8601 instead of ES5's definition.

In ES2015 (ES6), the specification was changed to align with ISO-8601:

If the time zone offset is absent, the date-time is interpreted as a local time.

Nevertheless, this change led to compatibility issues, especially with date-only formats like 2018-07-01. Subsequently, in ES2016, the interpretation was adjusted again:

When the time zone offset is absent, date-only forms are interpreted as UTC time and date-time forms are interpreted as local time.

For example, new Date("2018-07-01") is parsed as UTC, while new Date("2018-07-01T00") is parsed as local time.

These rules have remained consistent in ES2017 and upcoming ES2018 versions; you can refer to the current editor's draft for more details.

You can test your browser's behavior using the provided code snippet.

Current browser support status as of September 2021:

Modern Firefox, Chrome, and Safari browsers handle this correctly, including iOS browsers.
Interestingly, IE11 also interprets dates accurately.

Past browser support status as of April 2018:

IE11 handled dates correctly.
Firefox had accurate date interpretations.
Chrome 65 got it right on desktop and Android platforms.
However, there were issues with Chrome 64 (iOS) and iOS Safari in parsing date/time forms incorrectly as UTC.

An open issue related to date parsing in V8 engine from Chrome 64 to 65 has been resolved, but specific details are not readily available.

Answer 3

Answer №2

By ensuring that my server consistently sends DateTime objects to the client in a format that all browsers can interpret correctly, I am able to resolve the issue that is currently plaguing this app.

The key here is adding that 'Z' at the end of the DateTime object. It turns out that the ASP.NET MVC4 Json serializer, which is based on Json.NET, does not have Utc turned on by default. The default behavior for DateTimeZoneHandling is set to RoundtripKind, which does not include the 'Z' even when DateTime.Kind == Utc, causing frustration.

To address this issue, the solution is simple: adjust the way Json.NET handles timezones to use DateTimeZoneHandling.Utc:

var json = GlobalConfiguration.Configuration.Formatters.JsonFormatter;
// Ensure Utc formatting ('Z' at end). 
json.SerializerSettings.DateTimeZoneHandling = DateTimeZoneHandling.Utc;

Once this adjustment is made, all data transmitted from the server to the browser will be properly formatted as ISO-8601 with a trailing 'Z'. Testing has confirmed that all major browsers are able to handle this format accurately.

Answer 4

By ensuring that my server consistently sends DateTime objects to the client in a format that all browsers can interpret correctly, I am able to resolve the issue that is currently plaguing this app.

The key here is adding that 'Z' at the end of the DateTime object. It turns out that the ASP.NET MVC4 Json serializer, which is based on Json.NET, does not have Utc turned on by default. The default behavior for DateTimeZoneHandling is set to RoundtripKind, which does not include the 'Z' even when DateTime.Kind == Utc, causing frustration.

To address this issue, the solution is simple: adjust the way Json.NET handles timezones to use DateTimeZoneHandling.Utc:

var json = GlobalConfiguration.Configuration.Formatters.JsonFormatter;
// Ensure Utc formatting ('Z' at end). 
json.SerializerSettings.DateTimeZoneHandling = DateTimeZoneHandling.Utc;

Once this adjustment is made, all data transmitted from the server to the browser will be properly formatted as ISO-8601 with a trailing 'Z'. Testing has confirmed that all major browsers are able to handle this format accurately.

Answer 5

Answer №3

Encountering a similar issue prompted me to opt for interpreting the date with the local timezone rather than switching to "Z", especially for my specific use case. I devised a function that adds the local timezone information if it is absent in the ISO date. This function can serve as an alternative to using new Date(). It was inspired by the following explanation: How to ISO 8601 format a Date with Timezone Offset in JavaScript?

parseDate = function (/*String*/ d) {
    if (d.search(/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}$/) == 0) {
        var pad = function (num) {
            norm = Math.abs(Math.floor(num));
            return (norm < 10 ? '0' : '') + norm;
        },
        tzo = -(new Date(d)).getTimezoneOffset(),
        sign = tzo >= 0 ? '+' : '-';
        return new Date(d + sign + pad(tzo / 60) + ':' + pad(tzo % 60));
    } else {
        return new Date(d);
    }
}

Answer 6

Encountering a similar issue prompted me to opt for interpreting the date with the local timezone rather than switching to "Z", especially for my specific use case. I devised a function that adds the local timezone information if it is absent in the ISO date. This function can serve as an alternative to using new Date(). It was inspired by the following explanation: How to ISO 8601 format a Date with Timezone Offset in JavaScript?

parseDate = function (/*String*/ d) {
    if (d.search(/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}$/) == 0) {
        var pad = function (num) {
            norm = Math.abs(Math.floor(num));
            return (norm < 10 ? '0' : '') + norm;
        },
        tzo = -(new Date(d)).getTimezoneOffset(),
        sign = tzo >= 0 ? '+' : '-';
        return new Date(d + sign + pad(tzo / 60) + ':' + pad(tzo % 60));
    } else {
        return new Date(d);
    }
}

Answer 7

Answer №4

While David Hammond's answer is informative, it doesn't cover all the bases. Here is an enhanced version:

Supports fractional part in date/time string
Allows for optional seconds in date/time string
Takes daylight-saving time into consideration

appendTimezone = function (/*String*/ d) {
    // Identify ISO 8601 date-time strings with optional seconds and fractional part
    if (d.search(/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}(?::\d{2}(?:\.\d{1-3})?)?$/) == 0) {
        var pad = function (num) {
            norm = Math.abs(Math.floor(num));
            return (norm < 10 ? '0' : '') + norm;
        },
        tzo = -new Date(d).getTimezoneOffset(),
        sign = tzo >= 0 ? '+' : '-';

        var adjusted = d + sign + pad(tzo / 60) + ':' + pad(tzo % 60);

        // Check if timezone offsets are equal; adjust if needed
        if (-new Date(adjusted).getTimezoneOffset() != tzo) {
            tzo -= 60;
            adjusted = d + sign + pad(tzo / 60) + ':' + pad(tzo % 60);
        }

        return adjusted;
    } else {
        return d;
    }
}

parseDate = function (/*String*/ d) {
    return new Date(appendTimezone(d));
}

Answer 8

While David Hammond's answer is informative, it doesn't cover all the bases. Here is an enhanced version:

Supports fractional part in date/time string
Allows for optional seconds in date/time string
Takes daylight-saving time into consideration

appendTimezone = function (/*String*/ d) {
    // Identify ISO 8601 date-time strings with optional seconds and fractional part
    if (d.search(/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}(?::\d{2}(?:\.\d{1-3})?)?$/) == 0) {
        var pad = function (num) {
            norm = Math.abs(Math.floor(num));
            return (norm < 10 ? '0' : '') + norm;
        },
        tzo = -new Date(d).getTimezoneOffset(),
        sign = tzo >= 0 ? '+' : '-';

        var adjusted = d + sign + pad(tzo / 60) + ':' + pad(tzo % 60);

        // Check if timezone offsets are equal; adjust if needed
        if (-new Date(adjusted).getTimezoneOffset() != tzo) {
            tzo -= 60;
            adjusted = d + sign + pad(tzo / 60) + ':' + pad(tzo % 60);
        }

        return adjusted;
    } else {
        return d;
    }
}

parseDate = function (/*String*/ d) {
    return new Date(appendTimezone(d));
}

Answer 9

Answer №5

After reading @tig's useful response that provided exactly what I needed, here is a solution for .NetCore 1:

services.AddMvc();
services.Configure<MvcJsonOptions>(o =>
{
    o.SerializerSettings.DateTimeZoneHandling = DateTimeZoneHandling.Utc;
});

Alternatively,

services.AddMvc().AddJsonOptions(o => o.SerializerSettings.DateTimeZoneHandling = DateTimeZoneHandling.Utc);

For those using .NetCore 1.0.1:

services
    .AddMvcCore()
    .AddJsonFormatters(o => o...);

Answer 10

After reading @tig's useful response that provided exactly what I needed, here is a solution for .NetCore 1:

services.AddMvc();
services.Configure<MvcJsonOptions>(o =>
{
    o.SerializerSettings.DateTimeZoneHandling = DateTimeZoneHandling.Utc;
});

Alternatively,

services.AddMvc().AddJsonOptions(o => o.SerializerSettings.DateTimeZoneHandling = DateTimeZoneHandling.Utc);

For those using .NetCore 1.0.1:

services
    .AddMvcCore()
    .AddJsonFormatters(o => o...);

Chrome believes ISO time that lacks Z is in UTC; problem with C#

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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