The International Date Line zigzags to keep countries whole
Where today becomes tomorrow, the line bends hard to avoid splitting nations across two calendars.
The International Date Line marks where each calendar day begins. It roughly follows the 180 meridian, halfway around the globe from Greenwich — but it is emphatically not a straight line.
Instead it zigzags around landmasses. The line bends so that whole countries stay on a single date rather than waking up split between today and tomorrow. It detours east through the Bering Strait to keep Russia together and Alaska’s Aleutians with the United States, and it loops far out around the island nation of Kiribati.
The results can be startling. Across the Bering Strait, Cape Dezhnev, Russia is always a full day ahead of Cape Prince of Wales, Alaska — even though the two points sit less than 80 km (50 miles) apart.
Unlike the Prime Meridian, the date line has no treaty fixing its exact path. It’s a practical convention, redrawn whenever a nation decides its territory should all share the same day.
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