DateTime dt = DateTime.Now;  //本地时间
            string str0 = dt.ToString();
            Console.WriteLine(str0);  //2025-01-17 16:05:34
            //将本地时间输出为ISO 8601格式字符串，东八区后面会+08:00
            string str1 = dt.ToString("yyyy-MM-ddTHH:mm:sszzzz");
            Console.WriteLine(str1); //2025-01-17T16:05:34+08:00
            //将本地时间转成协调时间时（UTC）后输出为ISO 8601格式字符串，UTC时间后面会有个Z
            string str2 = dt.ToUniversalTime().ToString("yyyy-MM-ddTHH:mm:ssZ");
            Console.WriteLine(str2); //2025-01-17T08:05:34Z
            var dt0 = Convert.ToDateTime(str0); //ToDateTime可以把各类型的日期字符串转成本地时间
            var dt1 = Convert.ToDateTime(str1);
            var dt2 = Convert.ToDateTime(str2);
            Console.WriteLine("dt0=" + dt0);  //2025-01-17 16:05:34
            Console.WriteLine("dt1=" + dt1);  //2025-01-17 16:05:34
            Console.WriteLine("dt2=" + dt2);  //2025-01-17 16:05:34