Angular JS POST request not sending JSON data

If you are serializing your data object, it will not be a proper json object. Take what you have, and just wrap the data object in a JSON.stringify().

$http({
    url: '/user_to_itsr',
    method: "POST",
    data: JSON.stringify({application:app, from:d1, to:d2}),
    headers: {'Content-Type': 'application/json'}
}).success(function (data, status, headers, config) {
    $scope.users = data.users; // assign  $scope.persons here as promise is resolved here 
}).error(function (data, status, headers, config) {
    $scope.status = status + ' ' + headers;
});

I have tried your example and it works just fine:

var app = 'AirFare';
var d1 = new Date();
var d2 = new Date();

$http({
    url: '/api/test',
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    data: {application: app, from: d1, to: d2}
});

Output:

Content-Length:91
Content-Type:application/json
Host:localhost:1234
Origin:http://localhost:1234
Referer:http://localhost:1234/index.html
User-Agent:Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/29.0.1547.66 Safari/537.36
X-Requested-With:XMLHttpRequest
Request Payload
{"application":"AirFare","from":"2013-10-10T11:47:50.681Z","to":"2013-10-10T11:47:50.681Z"}

Are you using the latest version of AngularJS?

You can use FormData API https://developer.mozilla.org/en-US/docs/Web/API/FormData

var data = new FormData;
data.append('from', from);
data.append('to', to);

$http({
    url: '/path',
    method: 'POST',
    data: data,
    transformRequest: false,
    headers: { 'Content-Type': undefined }
})

This solution from http://uncorkedstudios.com/blog/multipartformdata-file-upload-with-angularjs

you can use your method by this way

var app = 'AirFare';
var d1 = new Date();
var d2 = new Date();

$http({
    url: '/api/apiControllerName/methodName',
    method: 'POST',
    params: {application:app, from:d1, to:d2},
    headers: { 'Content-Type': 'application/json;charset=utf-8' },
    //timeout: 1,
    //cache: false,
    //transformRequest: false,
    //transformResponse: false
}).then(function (results) {
    return results;
}).catch(function (e) {

});