using System;

using System.Collections.Generic;

using Newtonsoft.Json;

using Newtonsoft.Json.Converters;

​

public class Program

{

    public static void Main()

    {

        var people = new List<Person>

        {

            new Person { Name = "Grandpa", DateOfBirth = new DateTime(1925, 3, 2), DateOfDeath = new DateTime(2009, 10, 13) },

            new Person { Name = "Dad", DateOfBirth = new DateTime(1951, 7, 16), DateOfDeath = DateTime.MinValue }

        };

​

        var json = JsonConvert.SerializeObject(people, Formatting.Indented, new MinDateTimeConverter());

        Console.WriteLine(json);

        Console.WriteLine();

​

        var deserializedPeople = JsonConvert.DeserializeObject<List<Person>>(json, new MinDateTimeConverter());

        foreach (Person p in deserializedPeople)

        {

            Console.WriteLine("Name: " + p.Name);

            Console.WriteLine("DateOfBirth: " + p.DateOfBirth);

            Console.WriteLine("DateOfDeath: " + p.DateOfDeath);

            Console.WriteLine();

        }

    }

}

​

public class Person

{

    public string Name { get; set; }

    public DateTime DateOfBirth { get; set; }

    public DateTime DateOfDeath { get; set; }

}

​

public class MinDateTimeConverter : IsoDateTimeConverter

{

    public MinDateTimeConverter()

    {

        DateTimeFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss.fff'Z'";

    }

​

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)

    {

        if (objectType == typeof(DateTime) && reader.TokenType == JsonToken.Null)

            return DateTime.MinValue;

​

        return base.ReadJson(reader, objectType, existingValue, serializer);

    }

​

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)

    {

        if (value is DateTime date && date == DateTime.MinValue)

        {

            writer.WriteNull();

            return;

        }

        base.WriteJson(writer, value, serializer);

    }

}

​