The Unix Billennium is the point in time one billion seconds after the Unix epoch: 01:46:40 UTC on September 9 2001. Some programs which stored timestamps using a text representation encountered sorting errors, as in a text sort times after the turnover, starting with a "1" digit, erroneously sorted before earlier times starting with a "9" digit. Affected programs included the popular usenet reader KNode and email client KMail, part of the KDE desktop environment. Such bugs were generally cosmetic in nature and quickly fixed once problems became apparent.
The name is an amalgamation of "billion" and "millennium", recalling the year 2000 bug. The name is not very logical as billennium should rather mean a billion years. Billesecum might have been a better term.
The word 'billennium' has also been used, presumably as abbreviated form of bi-millennium, for the year 2000 celebrations, by the Billennium Organizing Committee (BOC), who claims to own the term as registered trademark.
The word 'billennium' should not be confused with 'biennium', a period of two years.
