var json2 = "{'dateAdded':1538207507,'lastModified':1538205295}";
            var bookmarks = JsonConvert.DeserializeObject<Test>(json2, new MyDateTimeConverter());

 public class Test
    {
        [JsonProperty(PropertyName = "dateAdded")]
        [JsonConverter(typeof(UnixDateTimeConverter))]
        public DateTime dateAdded;
        [JsonProperty(PropertyName = "lastModified")]
        [JsonConverter(typeof(UnixDateTimeConverter))]
        public DateTime lastModified;
        

        public Test(DateTime dateAdded, DateTime lastModified)
        {
            this.dateAdded = dateAdded.ToLocalTime();//當反序列化後時間因為時區的原因少8個小時
            this.lastModified = lastModified.ToLocalTime();
        }
    }
 

public class MyDateTimeConverter : Newtonsoft.Json.JsonConverter
    {
        public override bool CanConvert(Type objectType)
        {
            return objectType == typeof(DateTime);
        }

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            var t = long.Parse((string)reader.Value);
            return new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc).AddSeconds(t).ToLocalTime();//這裡轉換了時間，不知道為什麼沒用
        }

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            throw new NotImplementedException();
        }
    }