我就觉得没有关系，相加就等于两个数求和。

没有直接关系，就是把时间转成数字求和，例如：

mysql> select now() + now(), round((now() + now())/2), now();
+----------------+--------------------------+---------------------+
| now() + now()  | round((now() + now())/2) | now()               |
+----------------+--------------------------+---------------------+
| 40440418243114 |           20220209121557 | 2022-02-09 12:15:57 |
+----------------+--------------------------+---------------------+
1 row in set (0.01 sec)