public class X
{
    public DateTime Y { get; set; }
}

public static void SerializeProcess()
{
    var settings = new JsonSerializerSettings() {
                                        DateFormatHandling = DateFormatHandling.IsoDateFormat,
                                        DateTimeZoneHandling = DateTimeZoneHandling.Local };

    Console.WriteLine("SerializeProcess");
    Console.WriteLine("");

    string formatUTC;
    string formatLocal;
    string formatNonSpecified;

    X fromUtc = new X() { Y = new DateTime(2015, 1 ,1 , 18, 0, 0, 0, DateTimeKind.Local )  };
    X fromLocal = new X() { Y = DateTime.Now.ToLocalTime() };
    X fromNonSpecified = new X() { Y = DateTime.Now };

    formatUTC = JsonConvert.SerializeObject(fromUtc, settings);
    formatLocal = JsonConvert.SerializeObject(fromLocal, settings);
    formatNonSpecified = JsonConvert.SerializeObject(fromNonSpecified, settings);

    Console.WriteLine("fromUtc" + " " + formatUTC);
    Console.WriteLine("fromLocal" + " " + formatLocal);
    Console.WriteLine("fromNonSpecified" + " " + formatNonSpecified);

    Console.WriteLine("");
    Console.WriteLine("End - SerializeProcess");
    Console.WriteLine("");
}