asp.net core webapi 日期返回中出现字母T

// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddMvc()
        //全局配置Json序列化处理
        .AddJsonOptions(options =>
        {
              //设置时间格式
            options.SerializerSettings.DateFormatString = "yyyy-MM-dd";
        }
        );
}