IBM Support

Java SDK Time Zone Update Utility

General Page

The IBM Time Zone Update Utility for Java (JTZU) applies Daylight Saving Time (DST) changes directly to your Java SDKs and JREs.

IBM Time Zone Update Utility for Java: Version 1.7.24a.


JTZU updates the time zone information in IBM-supplied releases and service refreshes of the IBM SDK, Java Technology Edition and IBM Semeru Runtimes. With this tool, you can adopt changes to DST when you are unable to apply a service refresh, or when a service refresh or release is not yet available that incorporates the time zone changes you need.

JTZU searches your system for the IBM SDK, Java Technology Edition and IBM Semeru Runtimes and updates each one found. The tool works in two modes:

  1. Discovery mode identifies the Java instances that need updating and produces a detailed log file, which includes the current time zone levels.
  2. Patch mode updates Java instances to apply the DST changes. You must stop your Java applications when this process is running.

You can use JTZU to update individual Java instances or multiple instances on local or network drives. The update process can be run automatically without user intervention, or you can control which JREs and SDKs are updated. The flexibility built in to the tool means that you can adapt the way it runs to suit your needs. For further information about downloading, installing, and using JTZU, see the Readme file.

JTZU 1.7.24a delivers time zone changes for:

  • America/Miquelon
  • America/Toronto
  • Asia/Almaty
  • Asia/Ho_Chi_Minh
  • Asia/Gaza

JTZU is supported on AIX®, Solaris, HP-UX, Linux, Windows, macOS, and z/OS®. For more detailed information about the platforms supported and the SDKs and JREs discovered and updated by JTZU, see the Readme file.

DST changes can be applied to Java on IBM i systems using the TZUPATCH tool, which is included in the non-z/OS JTZU download package.

JTZU downloads

Platform JTZU download
AIX, Solaris, HP-UX, Linux, Windows, macOS, and IBM i jtzu-1.7.24a
z/OS jtzu-zos-1.7.24a

To see which time zone updates are included for different versions of JTZU, see Olson time zone updates for Java JRE and SDK service refreshes for IBM products.

Updates made to Java time zone data by JTZU are not managed by any of the formal change control mechanisms for servicing IBM software products.

Technical support

If you experience a problem using JTZU, check IBM Time Zone Update Utility (JTZU) known problems and diagnostic information. This document describes how to diagnose problems with JTZU and details the information that will be needed by the JTZU support team to help you.

For technical support on JTZU, including questions or feedback, send an e-mail to . This address is monitored on weekdays during normal working hours. We aim to reply within two working days.

If you have a licence that includes product support, you can also report problems using the standard IBM product support process. You must identify the IBM product being updated when the problem occurs.

Leap seconds

In coordinated universal time (UTC) a day normally consists of 86400 seconds. However, every few years there is an extra second called a “leap second”. The leap second is always added as the last second of the day, and always on December 31 or June 30. For example a leap second will be inserted at the end of June 30 2015.

The JVMs from IBM tolerate but do not utilize leap seconds, so they do not need updating with timezone data which has leap second information to work correctly. No action is required by customers to cope with the leap seconds.

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Document Information

Modified date:
15 February 2024