Impact of 2007 USA daylight saving changes on the Oracle database (Doc ID 359145.1)

Last updated on JULY 27, 2021

Applies to:

Oracle Database - Personal Edition - Version 8.1.5.0 to 10.2.0.1 [Release 8.1.5 to 10.2]
Oracle Database - Standard Edition - Version 8.1.5.0 to 10.2.0.1 [Release 8.1.5 to 10.2]
Oracle Database - Enterprise Edition - Version 8.1.5.0 to 10.2.0.1 [Release 8.1.5 to 10.2]
Information in this document applies to any platform.

Purpose

This is archived content made available during the USA DST 2007 update (DSTv3 and DSTv4).
If you are looking for information on applying DStv4 for upgrades to 10.2.0.4, 11.1.0.6 or 11.1.0.7 please see
<Note 553812.1> Actions for the DSTv4 update in the 10.2.0.4 patchset
<Note 829734.1> Actions for the DSTv4 update in the 11.1.0.6 base release
<Note 568125.1> Actions for the DSTv4 update in the 11.1.0.7 patchset
These notes are more effective and better to use for DST during upgrades.

For information about newer DST updates available, and which time zone definitions are updated, see the following note: <Note 412160.1> Updated Time Zones in Oracle Time Zone File patches

Under the Energy Policy Act of 2005, passed by US Congress and then signed into law by President George W. Bush on August 8 2005, the start and end dates of Daylight Saving Time (DST) in the US have been changed, starting in 2007.

The purpose of this document is to inform readers of possible changes that might be needed to Oracle databases because of these changes to DST rules.

For an overview of issues in all Oracle Database & other Server Technologies products please see primary <note 397281.1>.

An outline of the items discussed in this note can also be found in the following document on OTN:
http://www.oracle.com/technology/pub/notes/daylight-saving-time-update-guide.html
(this OTN document provides an outline and refers to this note for more information)

Scope

Time zone and DST information is used in Oracle in the following ways:

TIMESTAMP WITH LOCAL TIME ZONE (TSLTZ) and TIMESTAMP WITH TIME ZONE (TSTZ) datatypes (both as column types and in PL/SQL) and the TZ_OFFSET function provide time zone calculations. This time zone information comes from Oracle's time zone files, which are part of the database installation.
Patches exist to update the Oracle time zone files
The Oracle Java Virtual Machine (OJVM) uses time zone information embedded in the Oracle JVM in the database itself.
Patches exist to update the OJVM time zone information

Other datatypes, including DATEs, are not affected by changes to DST rules.
For more background information please see <Note:357056.1> (this is not needed to be read before proceeding with this note, it is only presented as a reference for background information).