how to force netwtonsoft json serializer to serialize datetime property to string?

From a post made by James Newton-King on StackOverflow, it looks like you can do this.

string isoJson = JsonConvert.SerializeObject(this, new IsoDateTimeConverter());
// {"Details":"Application started.","LogDate":"2009-02-15T00:00:00Z"}    

Referenced answer:
Parsing JSON DateTime from Newtonsoft’s JSON Serializer

Also here is the documentation on Json.NET and dates:
Serializing Dates in JSON

Here is an example of using the DateTimeFormat property to customize the output:

return JsonConvert.SerializeObject(this, Formatting.None, new IsoDateTimeConverter() { DateTimeFormat = "yyyy-MM-dd HH:mm:ss" });