How do I format a Microsoft JSON date?

#Updated

We have an internal UI library that has to cope with both Microsoft's ASP.NET built-in JSON format, like `/Date(msecs)/`, asked about here originally, and most JSON's date format including JSON.NET's, like `2014-06-22T00:00:00.0`. In addition we need to cope with [oldIE's inability to cope with anything but 3 decimal places][1].

We first detect what kind of date we're consuming, parse it into a normal JavaScript `Date` object, then format that out.

1) Detect Microsoft Date format

// Handling of Microsoft AJAX Dates, formatted like '/Date(01238329348239)/'
function looksLikeMSDate(s) {
return /^\/Date\(/.test(s);
}

2) Detect ISO date format

var isoDateRegex = /^(\d\d\d\d)-(\d\d)-(\d\d)T(\d\d):(\d\d):(\d\d)(\.\d\d?\d?)?([\+-]\d\d:\d\d|Z)?$/;

function looksLikeIsoDate(s) {
return isoDateRegex.test(s);
}

3) Parse MS date format:

function parseMSDate(s) {
// Jump forward past the /Date(, parseInt handles the rest
return new Date(parseInt(s.substr(6)));
}

4) Parse ISO date format.

We do at least have a way to be sure that we're dealing with standard ISO dates or ISO dates modified to always have three millisecond places ([see above](

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)), so the code is different depending on the environment.

4a) Parse standard ISO Date format, cope with oldIE's issues:

function parseIsoDate(s) {
var m = isoDateRegex.exec(s);

// Is this UTC, offset, or undefined? Treat undefined as UTC.
if (m.length == 7 || // Just the y-m-dTh:m:s, no ms, no tz offset - assume UTC
(m.length > 7 && (
!m[7] || // Array came back length 9 with undefined for 7 and 8
m[7].charAt(0) != '.' || // ms portion, no tz offset, or no ms portion, Z
!m[8] || // ms portion, no tz offset
m[8] == 'Z'))) { // ms portion and Z
// JavaScript's weirdo date handling expects just the months to be 0-based, as in 0-11, not 1-12 - the rest are as you expect in dates.
var d = new Date(Date.UTC(m[1], m[2]-1, m[3], m[4], m[5], m[6]));
} else {
// local
var d = new Date(m[1], m[2]-1, m[3], m[4], m[5], m[6]);
}

return d;
}

4b) Parse ISO format with a fixed three millisecond decimal places - much easier:

function parseIsoDate(s) {
return new Date(s);
}

5) Format it:

function hasTime(d) {
return !!(d.getUTCHours() || d.getUTCMinutes() || d.getUTCSeconds());
}

function zeroFill(n) {
if ((n + '').length == 1)
return '0' + n;

return n;
}

function formatDate(d) {
if (hasTime(d)) {
var s = (d.getMonth() + 1) + '/' + d.getDate() + '/' + d.getFullYear();
s += ' ' + d.getHours() + ':' + zeroFill(d.getMinutes()) + ':' + zeroFill(d.getSeconds());
} else {
var s = (d.getMonth() + 1) + '/' + d.getDate() + '/' + d.getFullYear();
}

return s;
}

6) Tie it all together:

function parseDate(s) {
var d;
if (looksLikeMSDate(s))
d = parseMSDate(s);
else if (looksLikeIsoDate(s))
d = parseIsoDate(s);
else
return null;

return formatDate(d);
}

The below old answer is useful for tying this date formatting into jQuery's own JSON parsing so you get Date objects instead of strings, or if you're still stuck in jQuery <1.5 somehow.

##Old Answer

If you're using jQuery 1.4's Ajax function with ASP.NET MVC, you can turn all DateTime properties into Date objects with:

// Once
jQuery.parseJSON = function(d) {return eval('(' + d + ')');};

$.ajax({
...
dataFilter: function(d) {
return d.replace(/"\\\/(Date\(-?\d+\))\\\/"/g, 'new $1');
},
...
});

In jQuery 1.5 you can avoid overriding the `parseJSON` method globally by using the converters option in the Ajax call.

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Unfortunately you have to switch to the older eval route in order to get Dates to parse globally in-place - otherwise you need to convert them on a more case-by-case basis post-parse.

[1]:

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