Thursday, 12 July 2007

Coming soon: 2007 Daylight Saving changes - The Sequel

I bought my quarterly train ticket just the other day. It expires in October. (I know that should be obvious, but we haven't had much sunshine here yet so it doesn't seem fair that autumn is so close.) That's depressing enough in itself, but I also just realised that the next round of Daylight Savings fun and games will soon be upon us.

For anyone who wasn't supporting Outlook a few months ago (or was in a country unaffected by the changes or just crawled under a rock and stayed there throughout March), the US government passed a piece of legislation in 2005 changing the dates the clocks "spring forward" and "fall back", starting from spring 2007. This gave three weeks more Daylight Saving time, and was calculated to save money and energy by people needing to use less heating and lighting.

Unfortunately, Windows only knows how to cope with one set of Daylight Saving Time (DST) rules per time zone. So, for instance, in London it knows we go into DST on the last Sunday in March, and we go back to GMT (Standard Time) on the last Sunday in October.

This might not sound like a problem, except that every time you schedule a recurring appointment in Outlook, it bases all future occurrences on what it knows about your time zone and DST settings now. So if those settings change, the meeting will appear to change. Which (as a lot of people found out) was exactly what happened.

This is a pretty complicated topic to explain. I spent the best part of three months this year talking about little else, and I still managed to get confused mid-presentation on more than one occasion! So for my own sanity and yours I'm going to stop now and leave the explanation of how Outlook saves appointments in UTC and displays them in local time for my next post.

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