Episode 1 of 1
Retrospective Day Zero Artifact
- When
- 1899-12-31 (retrospective convention)
- Where
- Software convention
Excel uses December 31, 1899, as day zero due to a deliberate bug compatibility feature inherited from Lotus 1-2-3.
The artifact arises because Lotus 1-2-3 incorrectly treated 1900 as a leap year to save memory. Excel replicates this error, including February 29, 1900, and treats December 31, 1899, as serial number 0, displayed as 0-jan-1900. This is a retrospective computing convention, not an event that occurred in 1899.
Sources
- Microsoft Excel Wikipedia, revision of 2026-08-26
- Lotus 1-2-3 Wikipedia, revision of 2026-07-26
Machine-drafted from the cited Wikipedia passages and checked by a reviewing model, not by a human editor. Every passage cites the revision it was written from; dates and places follow those passages.