Timezone changes best practices

Purpose

The purpose of this wiki document is to make the timezone related issues are addressed with respect to an SAP system. This document explains the different levels of timezone that is set in the SAP system.

Overview

At times its needed to adjust the SAP servers timezone when there is a daylight savings DST switch. During this time switch there needs to proper procedure followed to correct the timezones. SAP system and OS (Operating system) should be the same to avoid time differences and errors. In case if they are different then you may use the below reports to set them appropriately.

System Logic

The timezone is set at different levels of an SAP system.

1. Operating System Time  [CPU Clock Settings]
2. Time zone at Client         [Transaction Code STZAC]
3. User time zone               [Transaction Code SU01/SU3]

Changing the system time zone on SAP system should not have any influence on existing data, because the times/dates on database are stored with a certain time stamp and these are not influenced by the time zone changes. The sequence and the chronological order of the document will remain the same. In the transaction STZAC you do have the following two time zone input fields:

System Time Zone             <If an application is started in a client it can use this client time zone setting>

User's Default Time Zone   <If a user is connected to a client and for this userid if there is no time zone setting defined in the transaction SU01 of this client then the user time zone will be
                                            automatically set to the time zone value which is defined in this field here>

How to check the timezone at different levels

• Login to SAP system client  
• Run the report from Tcode SA38   -> TZCUSTHELP
• Run the report from Tcode SA38   -> RSDBTIME
• Run this function module in SE37   -> TZ_SYSTEM_GET_TZONE
• Run this report from Tocde SA38  -> TZONECHECK 

 Recommendation

• If you would like to update your system with the newest time zone data, then I would recommend to check note 198411 regularly.
• If you change timezone in STZAC it affects only the SAP instance timezone and only SAP system needs to be restarted.
• If you change the database time then you need to restart both SAP instance and Database Instance.
• Don't change the settings in STZAC when the users are connected to the system
• The 'System Time Zone' will be automatically changed for all clients but for the 'User's Default Time Zone' setting you have to start the   transaction STZAC in each specific client.
• We always recommend a downtime during the switch from daylight saving time to winter time to avoid issues during the so called "double hour".In this period the time does not run constantly and we cannot guarantee that the software can handle the situation if a point of time comes up twice.
• One possibility to avoid the downtime is the system time setting UTC. Then no daylight saving time switch is performed at all and so no downtime is needed.

Related Content

TZCUSTDISP     Display System Parameters for Time Zones
TZCUSTHELP    Troubleshooting Support for Time Zone Settings
TZONECHECK   Check Time Zone Data for Consistency
TZCUSTIM          Import Customizing Data
TZCUSTEX         Export Time Zone Data
RSDBTIME         Time diagnosis

Related Documents

Related SAP Notes

481835    Analyzing the time zone settings
198411    Current data and information about time zones
7417        Conversion between standard time and daylight saving
741734    Incorrect times due to the time zone settings
926290    SWNCCOLL: SAP workload NW collector collects no data

1375438  Globalization Collection Note > point 3

Fonte: https://wiki.scn.sap.com/wiki/display/Basis/Timezone+changes+best+practices