International Date Line

geography · time · ocean

Where Earth splits time. The International Date Line runs from the South Pole to the North Pole through the middle of the Pacific Ocean, roughly following the 180-degree line of longitude that sits directly opposite the Prime Meridian.

Crossing changes the date. If you sail or fly eastbound across the date line, you go back one calendar day. If you cross westbound, you jump forward one day, which means you could celebrate your birthday twice in one trip.

It wiggles around islands. The date line doesn't go perfectly straight because it curves around territories and island groups so people living on the same islands share the same date instead of being split between two different days.

Time is a human invention. The date line exists because humans invented calendar days and time zones to organize our lives, and we needed to pick one place on Earth where the day officially changes from one number to the next.