This guide explains the international date line in plain language, with the exact figures and how to work them out yourself.
The International Date Line zigzags through the Pacific near 180° longitude, marking where each calendar date begins and ends. Cross it heading west and you jump forward a day; cross heading east and you repeat one. A flight from Los Angeles to Sydney departs Tuesday and lands Thursday; the return can land before it took off, by the clock.
The line’s zigzag is political, not natural. It bulges to keep countries internally on one date — swinging around Russia’s far east, then between Alaska and Siberia (where Little Diomede and Big Diomede islands sit 3.8 km apart but nearly a day apart, the “Yesterday and Tomorrow” islands). In 1995, Kiribati moved the line eastward around its entire territory so the whole nation shared one date, creating the UTC+14 zone where each day on Earth begins. Samoa jumped across in 2011, skipping 30 December entirely to align its week with Australia and New Zealand.
Thanks to that spread — from UTC+14 down to UTC−12 — the same moment hosts three calendar dates on Earth for two hours daily, and every date takes about 50 hours from first light in Kiritimati to its last tick near Baker Island.
Add Kiritimati and Honolulu to the clocks at itsdately.com and you can watch a 24-hour date gap live between two Pacific islands — tomorrow and yesterday on one screen.
Frequently asked questions
Related on itsdately: Why Arizona Doesn't Change Its Clocks (Except Where It Does) · What Time Do Stock Markets Open Around the World? · How Railroads Invented Time Zones: The Day of Two Noons
Further reading: IANA Time Zone Database