How to parse a angular ui dateTime string to c# datetime

I know a lot of questions about this has been answered. I have tried for about 3 hours with no luck. I am using angular-ui datetime picker, the format is

"2015-02-08T06:00:00.000Z"

Error message is string was not recognized as a datetime

at System.DateTimeParse.ParseExact(String s, String format, DateTimeFormatInfo dtfi, DateTimeStyles style) at System.DateTime.ParseExact(String s, String format, IFormatProvider provider) at TransparentEnergy.Controllers.apiDocumentController.d__2.MoveNext() in c:\Development\TransparentEnergy\TransparentEnergy\ControllersAPI\apiDocumentController.cs:line 67

Controller

 string docDate = provider.FormData["DocumentDate"];
 model.DocumentDate = DateTime.ParseExact(docDate, "yyyy-MM-dd'T'HH:mm:ss'Z'", CultureInfo.GetCultureInfo("en-US"));

Angular-UI

 $scope.open = function ($event) {
    $event.preventDefault();
    $event.stopPropagation();

    $scope.opened = true;
};
$scope.formats = ['dd-MMMM-yyyy', 'yyyy/MM/dd', 'dd.MM.yyyy', 'shortDate'];
$scope.format = $scope.formats[3];

Update

 string docDate = provider.FormData["DocumentDate"];
            model.DocumentDate = DateTime.ParseExact(docDate, "yyyy-MM-dd'T'HH:mm:ss.fff'Z'", CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal);