Time Zone Changes for 2007 and ZCS
- 1 Overview
- 2 OS Vendors
- 3 ZCS 4.5.1
- 3.1 Web Client Users
- 3.2 Applying the OS time zone patch before upgrading to 4.5.1
- 3.3 Applying the OS time zone patch after upgrading to 4.5.1
- 3.4 Zimbra Connector for Outlook users
- 3.5 Zimbra Connector for iSync users
- 3.6 Zimbra Mobile users
- 3.7 REST users
- 3.8 Server Behavior
- 3.9 Server Patch Level
2007 brings changes to timezone definitions for the United States, Canada, Bermuda, and Australia. When an appointment is created it includes the dates to adjust for daylight savings and the offset from GMT. Appointments created with 2006's daylight savings transition dates will be incorrect for display of appointments in 2007 during the time where the offset from GMT is different for the two years.
Let's take the United States as an example. In 2007 daylight savings time starts 3 weeks earlier and ends 1 week later than it did in 2006. During these 4 weeks, recurring appointments created with the 2006 rules will be off by 1 hour. Also, single-instance appointments created using the 2006 rules for these 4 weeks will be off by an hour. Appointments that occur in the other 48 weeks of the year (including recurring appointments) are not impacted by the change since the 2006 and 2007 rules are the same for these weeks. A lot of the following text states "the appointment will display incorrectly". The incorrect display will occur only during these 4 weeks.
We are addressing these issues in two steps. The first is with 4.5.1, which includes updates with the 2007 rules and includes bug fixes for better time zone handling. The second step will include a server-based migration that will modify existing appointments to use the 2007 time zone definitions. Note that this migration is NOT included with 4.5.1.
Microsoft has provided an excellent article  describing the changes and how they impact its OS and products. We recommend all admins read it.
Before we go into the ZCS time zone behavior in 4.5.1, we should look at what the OS vendors have done to address these issues. Microsoft has issued a patch for Windows XP relating to KB article 931836. This patch updates OS time zone definitions for 2007. The patch does not change existing appointments in either the ZCO or the Zimbra Server. We hope that Microsoft will roll this patch out to all Windows XP machines, but to date that has not happened.
- Windows Vista shipped with the 2007 time zone definitions. This means that it is unnecessary to patch it.
- Apple included 2007 time zone definitions in OS X 10.4.6.
- Novell/SUSE and Red Hat have both provided patches for a variety of their offerings. IBM has produced an overview of Linux time zone issues that is well done and includes links for Linux fixes.
As you will see in the coming paragraphs, you must upgrade your desktops to these patch levels in order for time zone handling to work properly with ZCS 4.5.1. You can upgrade to ZCS 4.5.1 prior to deploying these patches to all of your desktops. However, for appointments to work correctly in these few weeks the OS patches must be present.
The sections below refer to "the OS time zone patch". This phrase refers to a patch provided by your OS vendor for the desktop computers of your users. It should be interpreted based on your OS. In summary:
- For Windows XP, it is the patch associated with KB article 931836.
- For Windows Vista, it is bundled.
- For Mac OS X, it is version 10.4.6 or later of the OS.
- For Linux, it is the updating of the zone info, which can be done independent of version.
With 4.5.1 the server will adjust the start time of existing appointments that occur in time zones that it recognizes when the appointment is accessed. But it will not permanently modify the appointment. The easiest way to describe what your users will experience is to examine behavior by OS and client type.
Web Client Users
Appointment Creation Without the OS time zone patch, appointments will be created that will be incorrect during the time period where the 2007 time zone definition is different from the old one. Note that these appointments will be created in a way such that the server migration script cannot later fix them to correctly use the 2007 time zone definitions.
With the OS time zone patch, the appointment will be created with a time zone definition that is correct for 2007.
Appointment Viewing With 4.5.1 existing appointments created by the web client and the Connector for iSync will be adjusted by the server to display as if they had the 2007 time zone definitions regardless of whether or not the patch was applied to the viewer's desktop. This means that the appointments will display correctly for users with the OS time zone patch, but incorrectly for users without the OS time zone patch.
Appointments that were created with 4.5.1 by web client users without the patch will display incorrectly across all clients.
Note that the server will not change existing appointments permanently. This means that sync-based clients (ZCO, iSync, Zimbra Mobile) will not get updated with the new time zone for the appointment, and sync clients will display the appointment at a different time than the web client. See the various sync client sections below for more information.
For all users, we recommend that admins update their users' desktops with the OS time zone patch before the upgrade to 4.5.1. Here are the alternatives:
Applying the OS time zone patch before upgrading to 4.5.1
With the patch and the 4.5.0 (or previous) release newly created appointments will reflect the 2007 time zone definition. The string identifier (e.g., GMT-0800, US/Pacific) will be incorrect, but the transition dates will be correct. Thus the appointment will display correctly in users' calendars. We regard this issue as a cosmetic annoyance, but not an issue with data.
Applying the OS time zone patch after upgrading to 4.5.1
Without the OS time zone patch and with 4.5.1 newly created appointments will conform to the 2006 time zone definition and will be constructed in a way such that they cannot be adjusted by the server on viewing. These appointments will render incorrectly for all clients. These appointments will also not be fixed by the server migration script we are going to provide.
Zimbra Connector for Outlook users
Since the calendar is synced locally its entries will not be adjusted by the 4.5.1 Zimbra Server. Users should first install the patch from KB article 928388. After doing that, they have 4 choices:
- Delete and re-create the impacted appointments. They will be created with the 2007 definition.
- Initial sync the mailbox. Most appointments will get recreated with the 2007 definition.
- Run the Outlook Time Zone Data Update Tool. This tool is provided by Microsoft and available at . This tool will update appointments in Outlook, and the ZCO will then push the updated appointments to the server. Once to the server, these changes will be propagated to other sync clients such as Zimbra Mobile.
- Wait for the server migration script. In this case the users will do nothing. Existing appointments will display incorrectly even with the patch and 4.5.1 until the server migration is run.
The point of installing the OS time zone patch for these users is that newly created appointments will be correct. Newly created appointments will be incorrect until the OS time zone patch is applied.
Zimbra Connector for iSync users
Generally Mac users that are running 10.4.6 will have their appointments automatically adjusted for 2007 time zone changes and they do not need to do anything more.
There are some cases where appointments will not display properly. For example, as noted above, if a web client user on a system without the OS time zone patch sends out an appointment with 4.5.1, that appointment will display incorrectly on the Mac.
Zimbra Mobile users
Our research suggests that most devices' calendar applications are using 2006 time zone definitions. Microsoft has provided a KB article on this issue for WM5, but the article targets OEM's and carriers. We recommend that you contact your carrier or manufacturer for patches appropriate to your phone. The implication of this is that appointments created on the device will display incorrectly on other clients.
Appointment Viewing. Appointments that exist in the device and were created with the 2006 timezone definitions will display incorrectly. The only available solution for this is to initial sync the device after upgrading the server to 4.5.1.
With the server migration script, the admin can update these appointments. This will cause the client to bring down the changes to the appointments, and they should then display correctly.
The REST interface will not adjust the appointments. It always returns the server's unadjusted view of the appointment. This means that existing appointments will be returned with 2006 time zone definitions until the forthcoming server migration script is run (or the appointments are recreated on a system with the OS time zone patch).
As mentioned earlier the 4.5.1 server attempts to fix time zone information that it recognizes as incorrect. Unfortunately, the server does not know about all possible time zone identifiers from all clients. Generally, the server will be able to fix appointments created by previous versions of the web client and the Zimbra Connector for iSync. It will not be able to fix appointments created by the Connector for Outlook nor Zimbra Mobile. It will also not be able to fix appointments created by the web client with version 4.5.1 (or later) on systems that do not have the OS time zone patch.
We are currently developing the server migration tool. We will release it as soon as possible.
Server Patch Level
We recommend that you update your server with the appropriate OS time zone patch. Please see the OS Vendors section above for the appropriate source for the patch.
Server Java Environment The required version of Java will be achieved if the above updates are performed.