Reg Exp
Web Design
Notes Client
Daylight Saving Time Changes
On August 8, 2005, President Bush signed into law a 1,724-page energy bill that, among other things, changes the starting and ending dates for daylight saving time (DST). Prior to 2007, DST starts on the first Sunday in April and ends on the last Sunday in October. Starting in 2007, DST will start on the second Sunday in March (3 weeks earlier) and end on the first Sunday in November (1 week later). What does this mean for your applications?

Well, it depends on your application and if you do any DST conversions. Most of the time, you hopefully rely on the operating system and/or Notes to do the conversion for you. Notes generally relies on the operating system to get time information. Microsoft is going to have to distribute a patch so DST will correctly adjust starting in 2007. So if you're relying on Notes (which relies on the operating system) then things should be fine. But you'll still need to look at your applications, just to be sure. Below are some examples.

Our mail scheduler product uses DST information for scheduling a message. Let's say you live in San Diego (Pacific Time, DST is observed) but your server is in Phoenix (Mountain Time, DST is NOT observed). If you have a message that is to be mailed every Sunday at 6 PM, that is the time of day according to you (6 PM Pacific Time). But that is different from the server time because of the time zone changes. Part of the year the message is to be mailed at 7 PM Phoenix time (when DST is not in place 7 PM Phoenix time is 6 PM Pacific time) and the other part of the year the message is to be mailed at 6 PM Phoenix time (when DST is in place Phoenix time and Pacific time are the same). The times of year when that switch happens will be affected by this change in DST starting and ending dates.

A second thing to keep in mind is that, as of now, US and Canada share time zones and DST settings. If Canada decides to keep the current settings, then certain parts of North America will change to DST 3 weeks earlier than other parts of North America. This may require additional time zones added to the operating system and/or to your application(s). Nothing has yet been published to indicate one way or another whether Canada will switch the DST starting and ending dates when the US changes in 2007.

Another instance is if you are using time zone fields. These are stored in Notes in a specific format, and the format includes the starting and ending dates for DST. For example, let's say you have a time zone field that is set to Eastern Time with DST in effect. Internally, the value is saved as:
Z=5$DO=1$DL=4 1 1 10 -1 1$ZX=25$ZN=Eastern

The "Z" part is how many hours before GMT the zone is (5 hours before - West - of GMT). The "DO" part being "1" means that DST is observed. The "DL" part is the rule for DST. The first 3 numbers are when it starts - month, week number, and day of the week. So this says that DST starts on the first Sunday in April. This will need to change to "3 2 1" to indicate that it's the second Sunday in March. The last three numbers are when it ends - month, week number, and day of the week. So "10 -1 1" says that it ends on the last (-1) Sunday in October. This will need to change to "11 1 1" to indicate that it's the first Sunday in November.

Will these values automatically change with your applications? Since I don't work for Lotus, I can't say for sure. But it's going to have to be addressed at some point before 2007.

There are some hints and tips on this web site that talk about DST. For example, there is a JavaScript function that computes the current time zone of the user and determines if DST is observed. That tip can be found here: http://www.breakingpar.com/bkp/home.nsf/0/87256B280015193F87256CFB006C45F7. That JavaScript will continue to work because the check for DST is made by checking the time difference from January 1st to July 1st. The changes in DST do not cross that boundary - it is still "summer time" and "winter time". And all the postings which have enhanced the original code (code that determines northern hemisphere and southern hemisphere, for example) should still be fine because January and July are compared.

So, for now you should just be aware that the change is coming and maybe take a look at what you might need to change. Some applications may have to change based on the energy bill. Other applications (like ones using the Notes Time Zone fields) may or may not have to change - it depends on what Lotus says in the future.