millennium bug

American

noun

Informal.

a bug that could cause computers or software to misinterpret a year after 1999 as having the first two digits 19 instead of 20, due to the coding of dates using only the last two digits of the four-digit year.

millennium bug British

noun

computing any software problem arising from the change in date at the start of the 21st century

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of millennium bug

First recorded in 1990–95

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

millennium bug

Twenty five years ago computer programmers were racing to fix the millennium bug amidst fears that it would cause banking systems to crash and planes to fall out of the sky.

From BBC ● Feb. 20, 2025

Throw in the kingdom-wide risk of plague – a different sort of millennium bug – and this could be a particularly pungent prequel.

From The Guardian ● Aug. 24, 2015

"I think there was a lot of hyperbole in the press. Part of our job was to keep on top of the hype" says Paddy Tipping, then minister for the millennium bug.

From BBC ● Dec. 30, 2014

“Right now it’s like the millennium bug all over again,” he said.

From New York Times ● May 28, 2012

A large part of the misunderstanding stems from Dionysius Exiguus--Latin for "Dennis the Short"--a 6th century monk who should be thought of as the original millennium bug.

From Time Magazine Archive

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023