Seding date as json response from web api to angularJS

Very simple question.

I am working on a angularjs app retrieving data from an asp.net web api. I have a date field (ThisDate) in a table (Model) which has date format like this -

2015-03-14 12:39:32.470

When I send this as a response json string from asp.net - 

string json = "{\"CreatedAt\": \"" + Model.ThisDate + "\"}";
response.Content = new StringContent(json, Encoding.UTF8, "application/json")

..I am getting it like this in angularjs app -

14-03-2015 12:39:32

And When I send it as a json serialized object from asp.net - 

JsonConvert.SerializeObject(Model)

..I am getting it like this in angularjs app -

2015-03-14T12:39:32.470

What are the reasons for this to be different? I want both to be in second format, so sorting works correctly. How to achieve this?

Thanks in advance.

I am still not sure why it converts they way it does. But I was able to fix this by specifying a sortable datetime format while sending response json string as below - 

string json = "{\"CreatedAt\": \"" + Model.ThisDate.ToString("s") + "\"}";

Refer here