Post a Comment On: stAllio!'s way

cory has a post on boingboing about DST and last weekend's "fall back". update 1, about the tz database is particularly interesting.

cory notes that "It's cool how many more of my clocks do this automatically with each passing year." and having lived for 4 years in a dst state (missouri), i can definitely appreciate the convenience of your clocks automatically adjusting themselves, saving you from the chore of remembering that it's changin' time and manually changing all the clocks in your house (of which there could be quite a few, what with clocks built into so many appliances these days).

but the boingboing post only hints at the technological hurdles involved whenever there's a change to dst observance. somebody out there has to write all the software so that our computers and clocks can automatically change themselves.

for example, windows has an "indiana" time zone setting that sets your computer at eastern standard time year-round. most computers in the state probably use that setting. but come april, that will be wrong, and all computers in indiana will have to be changed to either the "eastern" or "central" settings, depending where in the state they are. and that's just windows computers... older mainframes and legacy systems (which are the backbone of our information infrastructure) will require much more effort (and expense) to update. and it all must be done by april 2, or else bad things will happen to those systems.

also, while the boingboing quotes a passage from wikipedia that mentions offhand that the recently-passed energy policy act of 2005 will extend dst by a few weeks (snuck into the bill using extremely questionable "energy savings" numbers), it doesn't include this passage, which explains what an enormous pain in the ass this will be for the world's programmers and computer admins:

Starting March 11, 2007, daylight saving time will be extended another four to five weeks, from the second Sunday of March to the first Sunday of November. The change was introduced by the Energy Policy Act of 2005; the House had originally approved a motion that would have extended DST even further. Proponents claimed that the extension would save "the equivalent of" 10,000 barrels of oil per day, but this figure was based on U.S. Department of Energy information from the 1970s, the accuracy and relevance of which the DoE no longer stands by. There is very little recent research on what the actual positive effects, if any, might be. (See this article, for example.)

The extension, which puts the U.S. out of step with other countries in North America (for example Canada), was greeted by criticism from the airline industry and those concerned for the safety of children traveling to school in the dark before the late sunrise (see this article for example).

An additional issue raised by this extension is that it requires reconfiguration of virtually every computer in the United States. Most computers are programmed to adjust automatically for DST, but they do so based on static tables stored directly on the computer itself. In order to change the dates and times at which the automatic jump to or from DST occurs, these tables must be modified, which requires some sort of manual intervention by a human being in the great majority of cases. A two-minute procedure for updating a computer, multiplied by a hundred million computers, represents nearly 1700 years of full-time labor. More difficult to quantify is the amount of labor and money that may be spent correcting errors that arise due to a failure to update computers. Certain types of information systems (those that schedule future events with reference to UTC, for example) are almost guaranteed to encounter serious desynchronization problems unless both computers and databases are carefully updated—in some cases by hand.
hoosiers might be the only ones really howling about DST this year, but as march 2007 nears, a lot of geeks all over the place will start kvetching as well.

speaking of which, my last dst post has attracted a troll, who dusts off the old "if it's the most controversial issue in indiana then it must be the biggest problem in indiana" straw man, and suggests that "if you want to earn some respect from bloggers nationwide" i should "begin blogging about real issues"... for some reason i don't think that was a regular reader. but it might be my first troll.¶