Java JSONObject for .net webservice deserialisation to DateTime()

Question

I have a .net Webservice which should communicate with a Java app via json.

Now I have a method on the server side that looks like this:

    [WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public DateTime GetDate(DateTime input)
    {
        return input;
    }

from a C# app I can send a receive DateTime value. It's a convention that Date values are serialized as:

\/Date(1279176056000)\/

where the number is defined as seconds since epoch. So if I want to call that service my json request string must look like this:

{"input":"\/Date(1279176056000)\/"}

Howevery, I don't know how to achive that with the json.org.* classes on the Java side.
The problem: If I use this code:

JSONObject json = new JSONObject();
json.put("input", "\\/Date(1279176056000)\\/");

the JSONObject is smart enough to escape the string itself before sending it through the wire, so I get:

{"input":"\\/Date(1279176056000)\\/"}

which results in an Exception during server side deserialisation:

System.FormatException: \/Date(1279183256000)\/ is not a valid value for DateTime
bei System.ComponentModel.DateTimeConverter.ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, Object value)
bei System.Web.Script.Serialization.ObjectConverter.ConvertObjectToTypeInternal(Object o, Type type, JavaScriptSerializer serializer, Boolean throwOnError, Object& convertedObject)
bei System.Web.Script.Serialization.ObjectConverter.ConvertObjectToTypeMain(Object o, Type type, JavaScriptSerializer serializer, Boolean throwOnError, Object& convertedObject)
bei System.Web.Script.Serialization.ObjectConverter.ConvertObjectToType(Object o, Type type, JavaScriptSerializer serializer)
bei System.Web.Script.Services.WebServiceMethodData.StrongTypeParameters(IDictionary`2 rawParams)
bei System.Web.Script.Services.WebServiceMethodData.CallMethodFromRawParams(Object target, IDictionary`2 parameters)
bei System.Web.Script.Services.RestHandler.InvokeMethod(HttpContext context, WebServiceMethodData methodData, IDictionary`2 rawParams)
bei System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(HttpContext context, WebServiceMethodData methodData)

Long story short: How can I pass a backslash as a parameter to JSONObject without having it escaped?

Well, you might think I just just build the JSON string myself but I really want to send and receive more complex objects/arrays containing Date properties and I don't want to handle the whole JSON generation myself.