datetime and timezone

Hi All,

I just wanted to confirm what I've found:

A datetime field is not stored independent of timezone?

In otherwords, I have a java app that accesses MSSQL via JDBC. In java, the 'Timestamp' object is internally represented as GMT, but when printed, it looks at the timezone of the OS to determine how to display it.

I thought that MSSQL would be the same in this respect but it seems not to be...

I set a datetime field to, for example, 10:30 am. I then changed my OS's (win xp) timezone from eastern to central, then opened up sql server management studio. The datetime field still showed as 10:30 am.

Does this sound right or am I doing something wrong?

Thanks,

Martin

No, you are right.

You could use the server function to represent the UTC time using the GetUTCDate() function.

HTH, Jens K. Suessmeyer.

http://www.sqlserver2005.de

|||The stored/saved data should not be affected by the change in the system time zone. What's saved is saved. The display of the data is the job of the client app.|||

Thanks for the reply Oj & Jens,

Oj, in the example I gave, the client app is SQL Server Management studio. Wouldnt that handle a timezone change & display appropriately? Are you saying that an app other than SQL Server Management studio would, if properly written, display the time correctly? I also saw this behavior with sqlcmd. If a raw time is kept in the database, is it up to the client to somehow know what timezone the date was written as? In other words, I could write my client app to take the time I get from mssql & adjust it according to the current timezone, but how do I know what timezone the un-adjusted time is relative to? It seems to save the time however I write it, so if I write 6:00pm and I happen to be in EST, it gets saved in MSSQL as 6:00pm. How would the client app know that that time is relative to EST?

Also, Jens said that this is how it is. Are you guys contradicting each other or am I misunderstanding? Sorry if I'm unclear with any of this.

Thanks,

Martin

|||Well, it depends :-) This is a implementation detail, if you want to store the local time of the client you should use the client functionality to determine a datetime and write it to the database. if you store no information about the time zone, you will probably don′t know when the row was inserted compared to other rows, inderted in other time zones. if you don′t care about time zones, because you are only acting locally / regionally then you are fine. If you want to let the Server determine the time for you, you should use a server function rather than a client function, provoding a single source of date information.

-Jens.|||

Martin,

Workbench will just display the data as it is returned from the server. So, if the data was saved as 20010101, it will always be returned as 20010101. If it is returned as anything else, it would be a major data problem.

Getutcdate() function is not meant to convert your existing datetime data and returning it in UTC format. The function is meant for getting a datetime in UTC and store that into the database instead of getdate(). Please check book online for additional info.