time_t/64 to DateTime and back

        public static System.DateTime t_timeToDateTime(System.Int32 t_time)
        {
            return new System.DateTime(1970, 1, 1, 0, 0, 0).AddSeconds(t_time);
        }
        public static System.DateTime t_time64ToDateTime(System.Int64 t_time64)
        {
            return new System.DateTime(1970, 1, 1, 0, 0, 0).AddSeconds(t_time64);
        }
        public static System.Int32 DateTimeTot_time(System.DateTime DateTime)
        {
            return (System.Int32)(DateTime - new System.DateTime(1970, 1, 1, 0, 0, 0)).TotalSeconds;
        }
        public static System.Int64 DateTimeTot_time64(System.DateTime DateTime)
        {
            return (System.Int64)(DateTime - new System.DateTime(1970, 1, 1, 0, 0, 0)).TotalSeconds;
        }