Science · 6 pages · 12 min
Why the date line is a convention
The date line is an agreed place to change the civil date, not a seam in the Earth.
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From the opening
The International Date Line is a convention because a round Earth plus local solar time forces a seam somewhere, and nothing in the physics picks the longitude of that seam. Cross the line and the civil date changes by one day, so the calendar can stay single-valued everywhere else. The opening covers why a round trip needs a seam, why the seam sits in the Pacific, and what a bend around islands does.
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Inside
- Why a round trip needs a seam
- Why the seam sits in the Pacific
- What a bend around islands does
- Why the clocks themselves do not jump
- Where the idea stops applying
- A distinction worth keeping
Sources
- The International Date Line as a civil convention
- Circumnavigation and the missing day