Episode 4 of 4
Day of Two Noons
- When
- November 18, 1883
- Where
- Allegheny Observatory, Pittsburgh
Railroads readjusted clocks to the new five-zone system on November 18, 1883, triggered by a telegraph signal.
On Sunday, November 18, 1883, all United States and Canadian railroads readjusted their clocks and watches to reflect the new five-zone system. This was done on a telegraph signal from the Allegheny Observatory in Pittsburgh at exactly noon on the 90th meridian, known as 'The Day of Two Noons'.
Sources
- Standard time Wikipedia, revision of 2026-09-22
- Time zone Wikipedia, revision of 2026-10-06
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.