Making Waves: DST Means Work for You and Me

On March 11, 2007, Daylight Savings Time starts earlier than last year. Congress moved the date with a simple vote. Now you and I have to do all the dirty work to make our computerized world fall into place. Are you ready?

When I was 15 and enthused about ham radio, I bought from Allied Radio one of those 24-hour wall clocks and set it for Greenwich Mean Time. Yeah, I was that geeky. What that clock showed me is that all the fuss about time zones and daylight saving time is completely unnecessary. Why couldn’t the whole world run off one time and change their local school and work times to whatever they wanted? Does it really matter if they’re going to work at 0800 in London and we’re going to work at 1800 in San Diego? Instead, governments and corporations spend enormous resources tracking zone boundaries and daylight saving periods. DST serves only as a way to change the numbers on the clock, and is more meaningless the closer you get to the equator where sunrise and sunset times don’t change much. If safety and conservation are important at the upper latitudes, why don’t we just change the starting times of the school or work day to suit the daylight available?

In 1973, they messed with daylight saving time briefly because oil supplies were squeezed. They wanted more daylight in the afternoon so that we didn’t run so many lights at work. But what I remember is that we were suddenly getting up in utter dark, running the heat and lights at home an hour earlier than before. The problem was that at the 45th parallel, there was only so much daylight. At the time I worked at a small daytime only Class IV AM station in Oregon, and during December and January I would sometimes work weekends from the 8:30 AM sign-on to the 5:30 PM sign-off. According to Wikipedia, studies of the effects of DST have variously concluded savings of energy and traffic deaths as well as loss of savings to economic efficiency and increased energy peak loads at sunrise.

On March 11 this year, we’re changing from the usual early April changeover to DST to March 11. The United States change is part of the Energy Policy Act of 2005. Again the justification is to synchronize the workday to the hours of daylight available so that we are less dependent on Middle East oil.

The international ramifications are interesting. Canada decided to adopt the U.S. plan to move DST; Mexico did not. For the first time that I can remember, Tijuana will be in a different time zone from San Diego from March 11 until April 1. My station, XETV Fox 6, will be in the uncomfortable position of advertising programming times to its majority U.S. audience in Pacific Daylight Time, while the country of license observes Pacific Standard Time.

You may have work to do in preparation for March 11 this year. If you run Windows XP or Vista on the internet, you should be able to download their normal maintenance update to change the automatic DST switch date. If you run a machine isolated from the net, you’ll have to schedule a download or just change the time zone of the workstation in question.

It turns out that the Dallas Semiconductor real time clock (RTC) chips that control time in many computers have hard-coded DST changeover dates so that can’t be overcome except by manually changing the time or GMT offset.

You can program Macintosh computers to change automatically on the correct dates by editing the /etc/localtime file. Instructions can be found here. has a clock howto with DST information.

If you depend on Java runtime applications, see Sun’s DST FAQ. It appears that if you accept the Java RT update being pushed to your workstations this month, you should be okay.

You’d do well to look around for time-dependent systems that may need your intervention. Some vendors are offering software upgrades to automate the GMT offset at the new time. Triveni, for example, is asking $500 to upgrade its PSIP management software that includes revised DST changeover dates. If you have a collection of similarly needy boxes around your broadcast facility and you can’t get away with simply changing the GMT offset yourself, this time change is going to cost you.