MySQL now()的月份，日期，小时，分钟和秒返回0值，但年份值正确。问题与sysdate()，current_timestamp()相同。 current_date()和current_time()返回正确的值。
mysql-sql> select now();
+--------------------+
| now() |
+--------------------+
| 2018-00-00 0:00:00 |
+--------------------+
1 row in set (0.00 sec)
mysql-sql> select sysdate();
+--------------------+
| sysdate() |
+--------------------+
| 2018-00-00 0:00:00 |
+--------------------+
1 row in set (0.00 sec)
mysql-sql> select current_timestamp;
+--------------------+
| current_timestamp |
+--------------------+
| 2018-00-00 0:00:00 |
+--------------------+
1 row in set (0.00 sec)
mysql-sql> select current_date();
+----------------+
| current_date() |
+----------------+
| 2018-09-21 |
+----------------+
1 row in set (0.04 sec)
mysql-sql> select current_time();
+----------------+
| current_time() |
+----------------+
| 22:08:47 |
+----------------+
1 row in set (0.00 sec)
我在Windows 10.0.17134.167中使用MySQL 5.7。系统时区为IST（+5.30）
mysql-sql> SELECT NOW(), @@global.time_zone AS gtz, @@session.time_zone AS stz;
+--------------------+--------+--------+
| NOW() | gtz | stz |
+--------------------+--------+--------+
| 2018-00-00 0:00:00 | +05:30 | +05:30 |
+--------------------+--------+--------+
1 row in set (0.00 sec)