Daylight savings in Ingres

In article ,
robinskl@spot.Colorado.EDU (Karen Robinson) wrote:

>Anyways, I am looking for examples of how people have handled the 
>Daylight Savings Time conversion.  I have found that data entered
>during Standard Time is now showing up one hour ahead of what it
>should be.  Conversely, data entered during Standard Time also shows
>up one hour off.
>
>Additionally (or maybe it is still the same problem) I have found that
>dates, such as 23-apr-1992 16:44:00, are showing up now as 17:44:00.  
>I would have to do some research to be able to tell exactly when that
>data was entered, but it certainly looks like it was entered during
>Standard Time.  Now that it is being viewed during DST it is one hour
>off.
>
>The Tech Support solution is to turn off the DST correction in the 
>kernel, but I am looking for other workarounds.  Any information
>would be appreciated.
>
>Thanks in advance.
>--
>Karen Robinson
>Database Administrator
>National Snow and Ice Data Center
>University of Colorado at Boulder
>303.492.1504
>robinson@shiver.colorado.edu


Hi Karen.

Ingres always stores time values in Greenwich Mean time (GMT) format. The
II_TIMEZONE variable  specifies the delta between your local time and GMT.
In other words, Ingres applies a correction to the value you specify before
storing it in the database. You need to co-ordinate with your System Manager
and change the value of the II_TIMEZONE variable at the same time that the
System Time is changed. You also need to stop and re-start Ingres. There is
an Advisor Note that talks about this.

There is a very interesting "gotcha" with Daylight Savings Time that happens
when your database receives "batch feeds" that contain time-stamp data. If
one of these batch feeds was generated _before_ the System Time and
II_TIMEZONE were changed, and up-loaded _after_ the changes, you will end up
with bad data in your database. The solution is to use the "GMT" format for
specifying dates. Ingres does _not_ apply time-zone corrections to dates
specified in GMT format.

Hope this helps. Send me e-mail if you have further questions.

Ignatius Fernandez
MCI SystemHouse
ifernandez@shl.com
(707) 226 0786
Ingres Q & A
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