Starting February 1, 2025, new ApsaraDB RDS for MySQL instances use the standard time zone of their region as the default value of default_time_zone, instead of SYSTEM.
Does this affect your instance?
| Instance type | Storage type | Impact |
|---|---|---|
| New instances (created on or after February 1, 2025) | Any | Default value of default_time_zone changed from SYSTEM to the region's standard time zone |
| Existing instances | Local disk, default_time_zone = SYSTEM | Alibaba Cloud automatically updates the value between March 12, 2025 and May 30, 2025 |
| Existing instances | Cloud disk | No change |
Background
The default_time_zone parameter controls the time zone of an RDS instance. When set to SYSTEM, the instance inherits the time zone of its underlying host.
This dependency on the host time zone creates two risks:
Performance degradation: High-frequency use of
TIMESTAMP-type fields causes lock contention during time zone conversion, leading to performance fluctuations.Data inconsistency: For RDS instances using local disks, the primary and secondary instances may have different times in extreme scenarios, which can result in data inconsistency.
What's changing
Default value for new instances
Effective February 1, 2025, new RDS instances — regardless of storage type — use the standard time zone of their region as the default value of default_time_zone. For example, instances in the China (Shanghai) region default to Asia/Shanghai. For the full list of region time zones, see Time zones.
Permission restriction for local disk instances
Effective February 1, 2025, you can no longer set default_time_zone to SYSTEM on instances that use local disks. Accepted values are standard time zones only, such as +08:00 or Asia/Shanghai.
Automatic update for existing local disk instances
Between March 12, 2025 and May 30, 2025, Alibaba Cloud automatically updates default_time_zone for existing instances that use local disks and currently have the value set to SYSTEM. The update runs during the O&M window and sets the value to the time zone offset of the instance's region — for example, +08:00 for China (Shanghai).
No action is required. The update does not require a restart and does not interrupt your services.
Only the time zone calculation rules are updated. The operating system time and MySQL time field storage are not affected.
Specify a custom time zone
If the automatically assigned time zone does not meet your requirements, change it manually in the ApsaraDB RDS console. See Change the time zone.
A manual time zone change requires restarting the instance, which may interrupt services. Schedule the restart during off-peak hours and make sure your application is configured to reconnect automatically after a restart.