Two digits saved a few bytes per record — and cost the world $300B to undo

For decades, storing a year as two digits was good engineering. Memory and disk were expensive, the convention was universal, and every programmer knew the systems would be replaced long before 2000. They were not replaced. The code went into payroll, billing, air traffic, power grids and bank ledgers, and stayed there.

By the 1990s nobody knew where all of it was. Remediation meant auditing code nobody had read in twenty years, in languages the original authors had retired from, to find every place a year was stored short. The global effort ran for years and cost an estimated $300 billion — the largest coordinated software repair ever attempted.

At midnight almost nothing failed, and the argument began immediately over whether the money had been wasted. It is unfalsifiable by design: a prevented failure leaves no evidence. What is not in dispute is the arithmetic — two bytes per date, multiplied across forty years of records, cost $300B to add back.