MySQL Time Zone Settings & Troubleshooting: A Complete Guide

1. Introduction: Why MySQL Time Zone Settings Matter

1-1. Impact of Time Zone Setting Mistakes

1. Reservation time offsets

• In reservation systems, time zone offsets can cause reservation times to be recorded incorrectly, potentially leading to disputes with users.

1. Log data inconsistencies

• If system logs or error logs are recorded in different time zones, pinpointing the cause of an issue becomes difficult.

1. Analysis data errors

• When analysis relies on dates and times, using offset time data can lead to incorrect conclusions.

1-2. Article Purpose and Audience

• How to check the current time zone setting
• How to set it permanently and temporarily
• How to troubleshoot issues

2. Basic Knowledge About MySQL Time Zone Settings

2-1. Difference Between System Time and Time Zone

1. System Time (system_time_zone)

• The default time setting based on the OS time zone where the MySQL server is running. It may be reset when the server restarts.

1. Time Zone (time_zone)

• A time zone setting managed on the database side. It is applied during interactions with applications and when executing SQL queries.

2-2. How to Check the Current Time Zone Setting

-- Check system time
SELECT @@system_time_zone;

-- Check database time
SELECTtime_zone;

2-3. Uses of Time Zone Settings

• Unified management of server logs: Standardizing the time zone aligns the chronology of error logs and system logs.
• Multi‑time‑zone support: It enables applications to manage data across different time zones for global users.

3. Importing and Preparing Time Zone Data

3-1. Verifying the Time Zone Tables

SELECT * FROM mysql.time_zone_name;

3-2. Steps to Import Time Zone Data

1. Update the time zone data:

   sudo mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql -u root -p mysql

2. Verify after import:

   SELECT * FROM mysql.time_zone_name;

4. Persistent and Temporary Time Zone Configuration Methods

4-1. Temporary Time Zone Setting

How to Set

-- Set the session time zone to Japan Standard Time (JST)
SET time_zone = '+09:00';

SET time_zone = 'Asia/Tokyo';

Verifying the Setting

SELECT @@session.time_zone;

4-2. Persistent Time Zone Setting

Method 1: Specifying in the Configuration File

1. Open the MySQL configuration file (my.cnf or my.ini).
2. Add the following line to the [mysqld] section.

[mysqld]
default-time-zone = '+09:00'

[mysqld]
default-time-zone = 'Asia/Tokyo'

3. Restart MySQL to apply the configuration changes.

sudo systemctl restart mysql

4-3. Points to Consider When Changing Settings

1. Verify consistency with the application

• If the application sets its own time zone, ensure it is consistent with the server.

1. Ensure the time zone tables are up to date

• If the latest time zone data hasn’t been imported, errors may occur.

1. Be aware of time differences in logs and backups

• Existing log and backup files are based on the original time zone, so after changing, handle data carefully.

5. Application Integration and Configuration Considerations

5-1. Basics of Application Integration

PHP and MySQL Time Zone Settings

<?php
// PHP time zone setting
date_default_timezone_set('Asia/Tokyo');

// Time zone setting for MySQL connection
$db = new PDO('mysql:host=localhost;dbname=testdb', 'username', 'password');
$db->exec("SET time_zone = '+09:00'");
?>

Python and MySQL Time Zone Settings

import pymysql
import pytz
from datetime import datetime

# Specify time zone
tz = pytz.timezone('Asia/Tokyo')

# Database connection
connection = pymysql.connect(
    host='localhost',
    user='username',
    password='password',
    database='testdb',
    cursorclass=pymysql.cursors.DictCursor
)

with connection.cursor() as cursor:
    # Set time zone per session
    cursor.execute("SET time_zone = '+09:00'")
    # Test query
    cursor.execute("SELECT NOW()")
    result = cursor.fetchone()
    print("Current Time:", result['NOW()'])

5-2. Considerations When Setting Time Zones

1. Prevent Time Zone Mismatches

• If the server and application time zone settings differ, data integrity can be compromised.

2. Date Data Storage Formats

• When dealing with time zones, you be aware of the differences between the DATETIME and TIMESTAMP types.

-- Insert current time
INSERT INTO events (event_time) VALUES (NOW());

6. Troubleshooting and FAQ Section

6-1. Common Errors and Solutions

1. Error: “Unknown or incorrect time zone”

SET time_zone = 'Asia/Tokyo';

1. Check the current time zone data:

SELECT * FROM mysql.time_zone_name;

2. If the time zone data is empty, import it using the following command:

mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql -u root -p mysql

3. After importing, try setting it again.

2. Error: “System time zone differs from database time zone”

SET GLOBAL time_zone = '+09:00';

6-2. FAQ Section

Q1. Can the server and application use different time zones?

Q2. Can data stored in UTC be converted to local time?

SELECT CONVERT_TZ('2023-12-23 10:00:00', 'UTC', 'Asia/Tokyo') AS converted_time;

6-3. Troubleshooting Summary

• Common errors are caused by missing time zone data imports or mismatches with system settings.
• Use verification and correction commands to respond quickly when errors occur.
• The FAQ section addresses practical questions, ensuring even beginners can configure settings with confidence.

7. Summary and Next Steps

7-1. Article Key Takeaways

1. Importance of MySQL Time Zone Settings

• Time zone settings are essential for maintaining accuracy in reservation systems, log management, and data analysis.
• Misconfigurations can cause data drift or errors, so proper management is required.

2. Basic Knowledge and How to Verify Time Zones

• We understood the difference between system time and database time.
• We explained how to use SQL commands to check the current configuration.

3. Importing and Preparing Time Zone Data

• We demonstrated how to verify and import time zone data with concrete examples.

7-2. Best Practices and Operational Tips

1. Regularly Update Time Zone Data

• Periodically verify that you’re using the latest time zone data and update it as needed.

1. Validate Settings in a Test Environment

• Before making changes in production, always test them in a staging environment.

7-3. Taking the First Step Toward Practice

1. Set Up and Verify Your Environment

• Run the time zone verification command in your development environment.

1. Practice Changing Settings

• Try both temporary and permanent settings and observe how they behave.

1. Simulate Error Handling

• Apply the error‑handling techniques you learned from FAQs and troubleshooting to deepen your understanding.

7-4. Closing Message