Chronologically Incorrect

Seventy years ago, W. I. Thomas and Dorothy Swaine Thomas proclaimed one of sociology's most influential ideas: "If men define situations as real, they are real in their consequences." Their case in point was a prisoner who attacked people he heard mumbling absent-mindedly to themselves. To the deranged inmate, these lip movements were curses or insults. No matter that they weren't; the results were the same.

The Thomas Theorem, as it is called, now has a corollary. In a microprocessor-controlled society, if machines register a disordered state, they are likely to create it. For example, if an automatic railroad switching system mistakenly detects another train stalled on the tracks ahead and halts the engine, there really will be a train stalled on the tracks.

Today, the corollary threatens billions of lines of computer code and millions of pieces of hardware. Because they were written with years encoded as two digits (treating 1998 as 98), many of world's software programs and microchips will treat January 1, 2000, as the first day of the year 1900. Like the insane convict, they will act on an absurd inference. For purposes of payment, a person with a negative age may cease to exist. An elevator or an automobile engine judged by an embedded microprocessor to be overdue for inspection may be shut down. All of our vital technological and social systems are vulnerable to crippling errors. Correcting programs requires time-consuming close inspection by skilled programmers, custom-crafted solutions for virtually every computer system, and arduous testing--and time is running out.

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