The JSON spec allows integers, fractional numbers, strings, arrays, but when it comes to dates things are handled differently. There really is no date format in the JSON spec. Would be nice if every JSON date output would conform to ISO8601 :)

// Ruby
2011-07-14 19:43:37 +0100

//ISO 8601
2011-07-14T19:43:37+0100

// Javascript Date Object
new Date(1310669017000)

// Javascript built-in JSON object
2012-04-23T18:25:43.511Z

// .NET JavaScriptSerializer
Date(1310669017000)

// .NET DataContractJsonSerializer
Date(1335205592410-0500)

// Ruby

2011-07-14 19:43:37 +0100

//ISO 8601

2011-07-14T19:43:37+0100

// Javascript Date Object

new Date(1310669017000)

// Javascript built-in JSON object

2012-04-23T18:25:43.511Z

// .NET JavaScriptSerializer

Date(1310669017000)

// .NET DataContractJsonSerializer

Date(1335205592410-0500)

Some of these can easily be converted to a PHP timestamp using strtotime(), others require some more magic.

Here is a way to transform the .NET variant, something that has been haunting me in a current project ;)

preg_match('~(\d+)\d{3}((?:\+|-)\d+)~',  $date, $match);
$dt = new DateTime('@' . $match[1]);
$dt = new DateTime($dt->format('Y-m-d H:i:s') . ' ' . $match[2]);
$date =  strtotime($dt->format('r'));

preg_match('~(\d+)\d{3}((?:\+|-)\d+)~', $date, $match);

$dt = new DateTime('@' . $match[1]);

$dt = new DateTime($dt->format('Y-m-d H:i:s') . ' ' . $match[2]);

$date = strtotime($dt->format('r'));

Due to the wide usage of JSON as an exchange format, I really hope we will see a spec update in the future :)

JSON Date (.NET) to PHP timestamp

Alexander