MySQL Server maintains several time zone settings:MySQL服务器维护多个时区设置：

The session time zone setting affects display and storage of time values that are zone-sensitive. 会话时区设置会影响对区域敏感的时间值的显示和存储。This includes the values displayed by functions such as NOW() or CURTIME(), and values stored in and retrieved from TIMESTAMP columns. 这包括NOW()或CURTIME()等函数显示的值，以及存储在TIMESTAMP列中和从中检索的值。Values for TIMESTAMP columns are converted from the session time zone to UTC for storage, and from UTC to the session time zone for retrieval.TIMESTAMP列的值从会话时区转换为UTC进行存储，从UTC转换为会话时区进行检索。

The session time zone setting does not affect values displayed by functions such as UTC_TIMESTAMP() or values in DATE, TIME, or DATETIME columns. 会话时区设置不会影响UTC_TIMESTAMP()等函数显示的值或DATE、time或DATETIME列中的值。Nor are values in those data types stored in UTC; the time zone applies for them only when converting from TIMESTAMP values. 这些数据类型中的值也不以UTC存储；时区仅在从TIMESTAMP值转换时适用于它们。If you want locale-specific arithmetic for DATE, TIME, or DATETIME values, convert them to UTC, perform the arithmetic, and then convert back.如果您希望对DATE、TIME或DATETIME值进行特定于区域设置的算术运算，请将其转换为UTC，执行算术运算，然后再转换回来。

The current global and session time zone values can be retrieved like this:当前的全局和会话时区值可以按如下方式检索：

SELECT @@GLOBAL.time_zone, @@SESSION.time_zone;

timezone values can be given in several formats, none of which are case-sensitive:值可以以多种格式给出，但都不区分大小写：

Several tables in the mysql system schema exist to store time zone information (see Section 5.3, “The mysql System Schema”). mysql系统模式中存在几个表来存储时区信息（见第5.3节，“mysql系统架构”）。The MySQL installation procedure creates the time zone tables, but does not load them. To do so manually, use the following instructions.MySQL安装过程会创建时区表，但不会加载它们。要手动执行此操作，请使用以下说明。

If your system has its own zoneinfo database (the set of files describing time zones), use the mysql_tzinfo_to_sql program to load the time zone tables. 如果您的系统有自己的zoneinfo数据库（描述时区的文件集），请使用mysql_tzinfo_to_sql程序加载时区表。Examples of such systems are Linux, macOS, FreeBSD, and Solaris. 此类系统的示例包括Linux、macOS、FreeBSD和Solaris。One likely location for these files is the /usr/share/zoneinfo directory. 这些文件的一个可能位置是/usr/share/zoneinfo目录。If your system has no zoneinfo database, you can use a downloadable package, as described later in this section.如果您的系统没有zoneinfo数据库，您可以使用可下载的软件包，如本节稍后所述。

To load the time zone tables from the command line, pass the zoneinfo directory path name to mysql_tzinfo_to_sql and send the output into the mysql program. 要从命令行加载时区表，请将zoneinfo目录路径名传递给mysql_tzinfo_To_sql，并将输出发送到mysql程序中。For example:例如：

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

The mysql command shown here assumes that you connect to the server using an account such as root that has privileges for modifying tables in the mysql system schema. Adjust the connection parameters as required.这里显示的mysql命令假设您使用root等帐户连接到服务器，该帐户具有修改mysql系统模式中表的权限。根据需要调整连接参数。

mysql_tzinfo_to_sql reads your system's time zone files and generates SQL statements from them. mysql_tzinfo_to_sql读取系统的时区文件并从中生成sql语句。mysql processes those statements to load the time zone tables.mysql处理这些语句以加载时区表。

mysql_tzinfo_to_sql also can be used to load a single time zone file or generate leap second information:mysql_tzinfo_to_sql还可以用于加载单个时区文件或生成闰秒信息：

After running mysql_tzinfo_to_sql, restart the server so that it does not continue to use any previously cached time zone data.运行mysql_tzinfo_to_sql后，重新启动服务器，使其不再继续使用任何以前缓存的时区数据。

If your system has no zoneinfo database (for example, Windows), you can use a package containing SQL statements that is available for download at the MySQL Developer Zone:如果您的系统没有zoneinfo数据库（例如Windows），您可以使用MySQL开发者专区提供的包含SQL语句的包进行下载：

https://dev.mysql.com/downloads/timezones.html

To use an SQL-statement time zone package that you have downloaded, unpack it, then load the unpacked file contents into the time zone tables:要使用已下载的SQL语句时区包，请解压缩它，然后将解压缩的文件内容加载到时区表中：

mysql -u root -p mysql < file_name

Then restart the server.

When time zone rules change, applications that use the old rules become out of date. To stay current, it is necessary to make sure that your system uses current time zone information is used. For MySQL, there are multiple factors to consider in staying current:当时区规则更改时，使用旧规则的应用程序将过时。为了保持最新状态，有必要确保您的系统使用当前的时区信息。对于MySQL，保持最新状态需要考虑多个因素：

If you are uncertain whether named time zones are available, for use either as the server's time zone setting or by clients that set their own time zone, check whether your time zone tables are empty. The following query determines whether the table that contains time zone names has any rows:如果您不确定命名的时区是否可用，无论是作为服务器的时区设置还是由设置自己时区的客户端使用，请检查您的时区表是否为空。以下查询确定包含时区名称的表是否有任何行：

mysql> SELECT COUNT(*) FROM mysql.time_zone_name;
+----------+
| COUNT(*) |
+----------+
|        0 |
+----------+

A count of zero indicates that the table is empty. In this case, no applications currently are using named time zones, and you need not update the tables (unless you want to enable named time zone support). 计数为零表示表为空。在这种情况下，当前没有应用程序使用命名时区，您不需要更新表（除非您想启用命名时区支持）。A count greater than zero indicates that the table is not empty and that its contents are available to be used for named time zone support. 计数大于零表示表不为空，其内容可用于命名时区支持。In this case, be sure to reload your time zone tables so that applications that use named time zones can obtain correct query results.在这种情况下，请务必重新加载时区表，以便使用命名时区的应用程序可以获得正确的查询结果。

To check whether your MySQL installation is updated properly for a change in Daylight Saving Time rules, use a test like the one following. The example uses values that are appropriate for the 2007 DST 1-hour change that occurs in the United States on March 11 at 2 a.m.要检查MySQL安装是否针对夏令时规则的更改进行了正确更新，请使用以下测试。该示例使用适用于2007年3月11日凌晨2点美国夏令时1小时变化的值。

The test uses this query:测试使用此查询：

SELECT
  CONVERT_TZ('2007-03-11 2:00:00','US/Eastern','US/Central') AS time1,
  CONVERT_TZ('2007-03-11 3:00:00','US/Eastern','US/Central') AS time2;

The two time values indicate the times at which the DST change occurs, and the use of named time zones requires that the time zone tables be used. The desired result is that both queries return the same result (the input time, converted to the equivalent value in the 'US/Central' time zone).这两个时间值表示夏令时变化发生的时间，使用命名时区需要使用时区表。期望的结果是两个查询返回相同的结果（输入时间，转换为“美国/中部”时区的等效值）。

Before updating the time zone tables, you see an incorrect result like this:在更新时区表之前，您会看到这样的错误结果：

+---------------------+---------------------+
| time1               | time2               |
+---------------------+---------------------+
| 2007-03-11 01:00:00 | 2007-03-11 02:00:00 |
+---------------------+---------------------+

After updating the tables, you should see the correct result:更新表格后，您应该看到正确的结果：

+---------------------+---------------------+
| time1               | time2               |
+---------------------+---------------------+
| 2007-03-11 01:00:00 | 2007-03-11 01:00:00 |
+---------------------+---------------------+

Leap second values are returned with a time part that ends with :59:59. 闰秒值返回的时间部分以:59:59结尾。This means that a function such as NOW() can return the same value for two or three consecutive seconds during the leap second. 这意味着NOW()等函数可以在闰秒期间连续两到三秒返回相同的值。It remains true that literal temporal values having a time part that ends with :59:60 or :59:61 are considered invalid.确实，时间部分以:59:60或:59:61结尾的文字时间值被视为无效。

If it is necessary to search for TIMESTAMP values one second before the leap second, anomalous results may be obtained if you use a comparison with 'YYYY-MM-DD hh:mm:ss' values. 如果需要在闰秒前一秒搜索TIMESTAMP值，如果将其与'YYYY-MM-DD hh:MM:ss'值进行比较，可能会获得异常结果。The following example demonstrates this. It changes the session time zone to UTC so there is no difference between internal TIMESTAMP values (which are in UTC) and displayed values (which have time zone correction applied).以下示例演示了这一点。它将会话时区更改为UTC，因此内部TIMESTAMP值（以UTC为单位）和显示值（应用了时区校正）之间没有差异。

mysql> CREATE TABLE t1 (
a INT,
ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (ts)
);
Query OK, 0 rows affected (0.01 sec)

mysql> -- change to UTC
mysql> SET time_zone = '+00:00';
Query OK, 0 rows affected (0.00 sec)

mysql> -- Simulate NOW() = '2008-12-31 23:59:59'
mysql> SET timestamp = 1230767999;
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO t1 (a) VALUES (1);
Query OK, 1 row affected (0.00 sec)

mysql> -- Simulate NOW() = '2008-12-31 23:59:60'
mysql> SET timestamp = 1230768000;
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO t1 (a) VALUES (2);
Query OK, 1 row affected (0.00 sec)

mysql> -- values differ internally but display the same
mysql> SELECT a, ts, UNIX_TIMESTAMP(ts) FROM t1;
+------+---------------------+--------------------+
| a    | ts                  | UNIX_TIMESTAMP(ts) |
+------+---------------------+--------------------+
|    1 | 2008-12-31 23:59:59 |         1230767999 |
|    2 | 2008-12-31 23:59:59 |         1230768000 |
+------+---------------------+--------------------+
2 rows in set (0.00 sec)

mysql> -- only the non-leap value matches
mysql> SELECT * FROM t1 WHERE ts = '2008-12-31 23:59:59';
+------+---------------------+
| a    | ts                  |
+------+---------------------+
|    1 | 2008-12-31 23:59:59 |
+------+---------------------+
1 row in set (0.00 sec)

mysql> -- the leap value with seconds=60 is invalid
mysql> SELECT * FROM t1 WHERE ts = '2008-12-31 23:59:60';
Empty set, 2 warnings (0.00 sec)

To work around this, you can use a comparison based on the UTC value actually stored in the column, which has the leap second correction applied:为了解决这个问题，您可以使用基于实际存储在列中的UTC值的比较，该值应用了闰秒校正：

mysql> -- selecting using UNIX_TIMESTAMP value return leap value
mysql> SELECT * FROM t1 WHERE UNIX_TIMESTAMP(ts) = 1230768000;
+------+---------------------+
| a    | ts                  |
+------+---------------------+
|    2 | 2008-12-31 23:59:59 |
+------+---------------------+
1 row in set (0.00 sec)