Advisory: Daylight saving time coming to an island nation near you: Mauritius changes in October

[Please note that I have revised this blog post, as of 081808.]

As noted at http://www.afrol.com/articles/29955 late last month (July 23, 2008) and in L’Express newspaper, the government of Mauritius has decided to adopt Summer Time (as it’s known in Europe, aka daylight saving time) in the island nation of over 1 million. According to the announcements we’ve seen, the country will begin recognizing Summer Time in October of this year.

“Mauritius will be the first sub-Saharan African nation to do so, connecting the island more closely to tourist and business markets in Europe.

According to the official reports, DST in the “Star and Key of the Indian Ocean” will begin on October 26, 2008 and end on March 27, 2009.

(Interesting factoid: did you know that Mauritius (according to the Wikipedia entry) is believed to have been the only habitat of the extinct Dodo bird?)

According to the article in Afrol News…

“The use of Daylight saving time (DST) is mostly confined to countries located at high latitudes, including all Europe except Iceland and most of North America. In the southern hemisphere, DST is only used in southern South America (notably Chile and Argentina), New Zealand and some parts of Australia.

“In Africa, the use of DST is seldom and in most cases counterproductive, as the continent’s location close to the equator produces only very small differences in daylight in winter and summer. However, Morocco, Tunisia and Egypt follow European summer time, while DST earlier was tried out in countries such as South Africa, Madagascar, Botswana, Algeria, Libya, Sudan and Ghana. These experiments however did not last long and no sub-Saharan country now uses DST.

So, what should you do?

We suggest that customers and partners use Central European Time (CET) which in Windows appears as (GMT+1 Brussels, Copenhagen, Madrid, Paris) for Mauritius. This time zone matches to the DST rules being adopted by Mauritius and it matches the governments stated intent of being “aligned with that in Europe and the United States of America.”

[Updated 081808] Serve me a piece of humble pie. After a bit of research, it appears that the suggestion of CET/CEST won’t work. My error.

Here’s why:

Historically, the island nation has only briefly observed DST in the early 80’s, and since then has been DST free. Now, Mauritius will ‘spring forward’ one hour forward at to UTC+5:00 on October 26, 2008, and then fall back an hour to UTC+4:00 on March 29, 2009.

Currently, the UTC Offset for Central European Summer Time (CEST) is UTC +2:00 hours; falling back to Standard time will put Brussels back to Central European Time (CET) in late October to UTC +1:00 hour. In looking at our list of time zones and published DST rules, no other country in the southern hemisphere observes these rules: European nations (specifically CET/CEST in this case, currently recognizing Summer Time) have the opposite movements given they are in the northern hemisphere: as we know, summer shifts are different between northern (European Summer Time) and time zones in the southern hemisphere.

In the southern hemisphere, Abu Dhabi, Muscat and the closer Victoria (Seych.) are all UTC Offset +4 hours for Standard time zone, but none observe daylight saving time in 2008 (or beyond). And as I found no other adjacent TZ in Date & Time that is +4:00h today, it appears that there is no existing TZ in Windows that the country could use. [/update]

OK, the obvious question that was recently asked:

“So, will you add the name of “Mauritius” to that time zone in a future Windows update?”

[Updated & revised 081808] No, at present, Windows won’t update the time zone currently in place by adding the name of this country with a hotfix or other out of band update prior to the implementation of DST in October.

We’ll follow the lead of the country’s decision to follow “closely to tourist and business markets in Europe.” We will post guidance to inform customers that they may use ~~Central European Time (CET)~~ ‘Abu Dhabi, Muscat’ for Mauritius, and then on Oct 26, set their clocks manually ahead an hour as a work around, as we recommended for Argentina. We are considering options for how we will address the change in Mauritius in our December 2008 DST & Time Zone update.

We will issue more formal alerts on this news item this month as we have done for other countries that made late-breaking changes to the Microsoft DST & TZ Site, specifically on the DST Hot Topics and Latest News page. Note that other DST and time zone changes, the decision in Mauritius may impact customers doing business in and with the affected region.

[Update 091608: See my post re: the upcoming December 2008 Cumulative Update as Mauritius will be added in that release as a new time zone to Windows.]

As noted previously (and included on our Hot Topics site), Microsoft will continue to adhere to the published release cadence and issue the next update to DST rules and time zones in the December release. We will provide updates on the Microsoft DST & Time Zone site, issue appropriate alerts, and work with our subsidiaries to provide localized guidance based upon the work done we’ve done for other regions in the past (as we did for Argentina last year). We have started this effort to allow customers enough time and information to ensure that they make the appropriate plans for their organizations.

For additional information on planning for DST and TZ changes, please see these past articles:

Tags: Microsoft, Daylight Saving Time, Daylight Savings Time, RSS, DST, Mauritius.