Can MySQL convert a stored UTC time to local timezone?

Question

Can MySQL convert a stored UTC time to local timezon:ed time directly in a normal select statement?

Let's say you have some data with a timestamp (UTC).

CREATE TABLE `SomeDateTable` (
  `id`    int(11) NOT NULL auto_increment,
  `value` float NOT NULL default '0',
  `date`  datetime NOT NULL default '0000-00-00 00:00:00',
  PRIMARY KEY  (`id`)
)

Then when I

"select value, date from SomeDateTable";

I of course get all the dates as in their stored UTC form.

But let's say that I would like to have them in another timezone (with DST), can I then add some magic to the select query so that I get all the dates back in the selected timezone?

"select value, TIMEZONE(date, "Europe/Berlin") from SomeDateTable";

Or must I do this in some other layer on top, like in some php code? (it seems to be how most people have solved this problem).

Thanks Johan

---

If your MySQL installation allows you to use CONVERT_TZ it is a very clean solution, this example shows how to use it.

SELECT CONVERT_TZ( '2010-01-01 12:00', 'UTC', 'Europe/Stockholm' )

However I don't know if this is a good way since some MySQL installation is missing this function, use with care.

Answer 1

Yup, the convert_tz function.

http://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html#function_convert-tz

Answer 2

For those unable to configure the mysql environment (e.g. due to lack of SUPER access) to use human-friendly timezone names like "America/Denver" or "GMT" you can also use the function with numeric offsets like this:

CONVERT_TZ(date,'+00:00','-07:00')

Answer 3

select convert_tz(now(),@@session.time_zone,'+03:00')

For get the time only use:

time(convert_tz(now(),@@session.time_zone,'+03:00'))

Answer 4

I propose to use

SET time_zone = 'proper timezone';

being done once right after connect to database. and after this all timestamps will be converted automatically when selecting them.

Answer 5

I am not sure what math can be done on a DATETIME data type, but if you are using PHP, I strongly recommend using the integer-based timestamps. Basically, you can store a 4-byte integer in the database using PHP's time() function. This makes doing math on it much more straightforward.

Answer 6

One can easily use

CONVERT_TZ(your_timestamp_column_name, 'UTC', 'your_desired_timezone_name')

For example:

CONVERT_TZ(timeperiod, 'UTC', 'Asia/Karachi')

Plus this can also be used in WHERE statement and to compare timestamp i would use the following in Where clause:

WHERE CONVERT_TZ(timeperiod, 'UTC', '{$this->timezone}') NOT BETWEEN {$timeperiods['today_start']} AND {$timeperiods['today_end']}