ASP.NET MVC JsonResult Date Format

Just to expand on casperOne's answer.

The JSON spec does not account for Date values. MS had to make a call, and the path they chose was to exploit a little trick in the javascript representation of strings: the string literal "/" is the same as "\/", and a string literal will never get serialized to "\/" (even "\/" must be mapped to "\\/").

See http://msdn.microsoft.com/en-us/library/bb299886.aspx#intro_to_json_topic2 for a better explanation (scroll down to "From JavaScript Literals to JSON")

One of the sore points of JSON is the lack of a date/time literal. Many people are surprised and disappointed to learn this when they first encounter JSON. The simple explanation (consoling or not) for the absence of a date/time literal is that JavaScript never had one either: The support for date and time values in JavaScript is entirely provided through the Date object. Most applications using JSON as a data format, therefore, generally tend to use either a string or a number to express date and time values. If a string is used, you can generally expect it to be in the ISO 8601 format. If a number is used, instead, then the value is usually taken to mean the number of milliseconds in Universal Coordinated Time (UTC) since epoch, where epoch is defined as midnight January 1, 1970 (UTC). Again, this is a mere convention and not part of the JSON standard. If you are exchanging data with another application, you will need to check its documentation to see how it encodes date and time values within a JSON literal. For example, Microsoft's ASP.NET AJAX uses neither of the described conventions. Rather, it encodes .NET DateTime values as a JSON string, where the content of the string is /Date(ticks)/ and where ticks represents milliseconds since epoch (UTC). So November 29, 1989, 4:55:30 AM, in UTC is encoded as "\/Date(628318530718)\/".

A solution would be to just parse it out:

value = new Date(parseInt(value.replace("/Date(", "").replace(")/",""), 10));

However I've heard that there is a setting somewhere to get the serializer to output DateTime objects with the new Date(xxx) syntax. I'll try to dig that out.

The second parameter of JSON.parse() accepts a reviver function where prescribes how the value originally produced by, before being returned.

Here is an example for date:

var parsed = JSON.parse(data, function(key, value) {  if (typeof value === 'string') {    var d = /\/Date\((\d*)\)\//.exec(value);    return (d) ? new Date(+d[1]) : value;  }  return value;});

See the docs of JSON.parse()

Here's my solution in Javascript - very much like JPot's, but shorter (and possibly a tiny bit faster):

value = new Date(parseInt(value.substr(6)));

"value.substr(6)" takes out the "/Date(" part, and the parseInt function ignores the non-number characters that occur at the end.

EDIT: I have intentionally left out the radix (the 2nd argument to parseInt); see my comment below. Also, please note that ISO-8601 dates are preferred over this old format -- so this format generally shouldn't be used for new development.

For ISO-8601 formatted JSON dates, just pass the string into the Date constructor:

var date = new Date(jsonDate); //no ugly parsing needed; full timezone support

There are quite a bit of answers to handle it client side, but you can change the output server side if you desired.

There are a few ways to approach this, I'll start with the basics. You'll have to subclass the JsonResult class and override the ExecuteResult method. From there you can take a few different approaches to change the serialization.

Approach 1:The default implementation uses the JsonScriptSerializer. If you take a look at the documentation, you can use the RegisterConverters method to add custom JavaScriptConverters. There are a few problems with this though: The JavaScriptConverter serializes to a dictionary, that is it takes an object and serializes to a Json dictionary. In order to make the object serialize to a string it requires a bit of hackery, see post. This particular hack will also escape the string.

public class CustomJsonResult : JsonResult{    private const string _dateFormat = "yyyy-MM-dd HH:mm:ss";    public override void ExecuteResult(ControllerContext context)    {        if (context == null)        {            throw new ArgumentNullException("context");        }        HttpResponseBase response = context.HttpContext.Response;        if (!String.IsNullOrEmpty(ContentType))        {            response.ContentType = ContentType;        }        else        {            response.ContentType = "application/json";        }        if (ContentEncoding != null)        {            response.ContentEncoding = ContentEncoding;        }        if (Data != null)        {            JavaScriptSerializer serializer = new JavaScriptSerializer();            // Use your custom JavaScriptConverter subclass here.            serializer.RegisterConverters(new JavascriptConverter[] { new CustomConverter });            response.Write(serializer.Serialize(Data));        }    }}

Approach 2 (recommended):The second approach is to start with the overridden JsonResult and go with another Json serializer, in my case the Json.NET serializer. This doesn't require the hackery of approach 1. Here is my implementation of the JsonResult subclass:

public class CustomJsonResult : JsonResult{    private const string _dateFormat = "yyyy-MM-dd HH:mm:ss";    public override void ExecuteResult(ControllerContext context)    {        if (context == null)        {            throw new ArgumentNullException("context");        }        HttpResponseBase response = context.HttpContext.Response;        if (!String.IsNullOrEmpty(ContentType))        {            response.ContentType = ContentType;        }        else        {            response.ContentType = "application/json";        }        if (ContentEncoding != null)        {            response.ContentEncoding = ContentEncoding;        }        if (Data != null)        {            // Using Json.NET serializer            var isoConvert = new IsoDateTimeConverter();            isoConvert.DateTimeFormat = _dateFormat;            response.Write(JsonConvert.SerializeObject(Data, isoConvert));        }    }}

Usage Example:

[HttpGet]public ActionResult Index() {    return new CustomJsonResult { Data = new { users=db.Users.ToList(); } };}

Additional credits:James Newton-King