Sql-server – WorldWide site – should I save UTC or in fixed time

sql serverutc-time

Let's say I have a world wide website ( I mean it has uses from all around the world).

I have 1 server which is in germany ( at some city). it will never be moved from germany – ever.

My question is :

When users saves data , I need to save the action date :

Should I save ( and I think I do) it as UTC ?

Or since – the server is in one location – it is ok to save all the dates as GetDATE()
so the point of relativity is the same point.

Am I wrong ? If I do , can you please supply a simple scenario where it's gonna fail ?

Best Answer

Always store data in the database in UTC and then use the appropriate timezone to convert it during display, in the application. Is the only sensible approach when it comes to consider data mobility (geo-replication), user location and , most importantly, daylight savings. If you store local time there will be times when you cannot distinguish between column values and you cannot order them properly due to daylight savings. Think that, in Germany, Oct. 27th 2:05 am will happen twice this year... And that is an easy case compared to, say, Morocco.

Related Solutions

MySQL – Set UTC Time as Default Timestamp

To go along with @ypercube's comment that CURRENT_TIMESTAMP is stored as UTC but retrieved as the current timezone, you can affect your server's timezone setting with the --default_time_zone option for retrieval. This allows your retrieval to always be in UTC.

By default, the option is 'SYSTEM' which is how your system time zone is set (which may or may not be UTC!):

mysql> SELECT @@global.time_zone, @@session.time_zone;
+--------------------+---------------------+
| @@global.time_zone | @@session.time_zone |
+--------------------+---------------------+
| SYSTEM             | SYSTEM              |
+--------------------+---------------------+
1 row in set (0.00 sec)

mysql> SELECT CURRENT_TIMESTAMP();
+---------------------+
| CURRENT_TIMESTAMP() |
+---------------------+
| 2012-09-25 16:28:45 |
+---------------------+
1 row in set (0.00 sec)

You can set this dynamically:

mysql> SET @@session.time_zone='+00:00';
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT @@global.time_zone, @@session.time_zone;
+--------------------+---------------------+
| @@global.time_zone | @@session.time_zone |
+--------------------+---------------------+
| SYSTEM             | +00:00              |
+--------------------+---------------------+
1 row in set (0.00 sec)

Or permanently in your my.cnf:

[mysqld]
**other variables**
default_time_zone='+00:00'

Restart your server, and you will see the change:

mysql> SELECT @@global.time_zone, @@session.time_zone;
+--------------------+---------------------+
| @@global.time_zone | @@session.time_zone |
+--------------------+---------------------+
| +00:00             | +00:00              |
+--------------------+---------------------+
1 row in set (0.00 sec)

mysql> SELECT CURRENT_TIMESTAMP();
+---------------------+
| CURRENT_TIMESTAMP() |
+---------------------+
| 2012-09-25 20:27:50 |
+---------------------+
1 row in set (0.01 sec)

SQL Server – How to Get Correct Offset Between UTC and Local Times

The best way to convert a non-current UTC date into local time, prior to SQL Server 2016, is to use the Microsoft .Net Common Language Runtime, or CLR.

The code itself is easy; the difficult part is usually convincing people that the CLR isn't pure evil or scary...

For one of the many examples, check out Harsh Chawla's blog post on the topic.

Unfortunately, there is nothing built-in prior to SQL Server 2016 that can handle this type of conversion, save for CLR-based solutions. You could write a T-SQL function which does something like this, but then you'd have to implement the date-change logic yourself, and I'd call that decidedly not easy.

Best Answer

Related Solutions

MySQL – Set UTC Time as Default Timestamp

SQL Server – How to Get Correct Offset Between UTC and Local Times

Related Question