Announcement: Coming in December: Microsoft Updates to Daylight Saving Time and Time Zones

Clip art from Office Online First off, I want to welcome Lourdes to the DST blog over at  She is coordinating the efforts on our daylight saving time and time zone updates and releases for current products across the various product groups at Microsoft.  A tough job, to say the least.  She will also help coordinate messaging and communications with many other folks you may remember across our product groups, field sales and technical account teams, customer support and execs.  It’s great to have her on board.

I wanted to provide some insight as to the effort we just kicked off the planning for our December 2008 cumulative time zone update for Microsoft Windows operating systems and other products. (You may recall that the Windows Sustained Engineering team completed and released KB 951072, the August 2008 cumulative time zone update for Microsoft Windows operating systems.)  I also posted this to Twitter as it appears on my various social networking updates – we’ll see how effective these updates are for folks.

As we update the Microsoft daylight saving time and time zone help and support pages at, I expect that other product teams at Microsoft will also provide information on their products and publish the associated documentation (KBs, blog posts) in the November and early December time frame.  Groups will note any changes and updates in their documentation, products and services, and guidance for their support teams and the field.

So, back to the December 2008 release.

Coming soon are updates to the list of Microsoft products affected by DST and time zone changes.  We also have a number of new update notices on the DST Hot Topics and Latest News page, namely updates on the countries noted below; as noted, we’re still waiting for a confirmation on changes proposed for Iran and Argentina.  In some cases, Windows will release hotfixes for specific regions (including Brazil, Egypt) prior to the changes in those countries: watch the DST Hot Topics page and our blogs for more information.

Here’s a list of the DST and TZ updates planned for the December release: thanks to Joel, Steve, Jennifer, Shay and Sophia for helping collect and review the information (and to Clarence for reminding me today that countries really should implement time changes at 2:00AM rather than midnight):

DST & Time Zone updates coming in December 2008

* – Mauritius is a new time zone to be added to Windows in December 2008.

Here’s a text version of the table:


Time Zone Standard name

DST start

DST end


Mauritius Standard Time

Last Sunday in October at 02:00:00

Last Sunday in March at 02:00:00


Egypt Standard Time

Last Thursday in April at 23:59:59

Last Thursday in August at 23:59:59


E. South America Standard Time

Third Sunday in October at 00:00:00

Second Sunday in February at 00:00:00


Central Brazilian Standard Time

Third Sunday in October at 00:00:00

Second Sunday in February at 00:00:00


Pakistan Standard Time

First Sunday in June at 00:00:00

Last Friday in October at 23:59:59.


Pacific SA Standard Time

Second Saturday in October at 23:59:59

Second Saturday in March at 23:59:59


Iran Standard Time

Not yet confirmed

Not yet confirmed


Argentina Standard time

Not yet confirmed

Not yet confirmed


Morocco Standard Time

Last Saturday in May at 23:59:59

Last Sunday in August at 23:59:59.

Please note that where we have heard that changes may be coming to a territory but have yet to receive an official confirmation from a government, we indicate that the changes are "not yet confirmed."

As a reminder on our annual cadence (outlined here) and in a prior post, our product teams are moving to an annual product update cadence (with provisions for semi-annual as needed).  Following the Windows regular cadence for publishing newly legislated DST rules and time zone updates, our "Cumulative DST and Time Zone Updates" will be released in November/ December (to the Download Centre and via Windows Update respectively) for the coming calendar year; we’ll also provide for a semi-annual update in the July/August timeframe when needed. 

For each, the window closes for additional updates a few months (generally four to six) prior to the release date. 

As I originally posted here, most Windows applications (and some services) reference the underlying OS for DST and time zone information, but some do not. The product and service groups with offerings that have internal DST or TZ references have agreed to follow the regular schedule for cumulative Windows OS DST & TZ updates. The regular Windows release provide a regular schedule for other product groups to follow, as noted in the DST & TZ Product Update Cadence policy. We hope that this will provide a more predictable way for our customers to anticipate and plan for our cumulative updates

This year (as in 2006 and 2007) the Windows team plans to release the packages to the Microsoft Download Center in November and then to Windows Update in early December.  They will also publish the new or modified TZI keys in an update to Microsoft KB article 914387 for IT professionals and sysadmins who may need that information.  Our goal is that our customers and partners can plan on rolling out and installing/ deploying these regular, scheduled cumulative update roll-ups as they are published.

Let us know if you have questions.

Tags: Microsoft, Daylight Saving Time, Daylight Savings Time, RSS, DST, Mauritius, Morocco, Brazil, Pakistan; 4,400,000 (up from 3.6M a week ago); 2,330,000 (up from 900K a year ago); 1,472,886

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[edits 091608: replaced table with graphic, cleaned up typos]

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