Geography
The Significance of the International Date Line in Global Timekeeping
Quick fact
The International Date Line is not a straight line; it zigzags around island nations to keep entire countries on the same date, and it is a political convention as much as a geographical one.
Why this is interesting
If you travel east across the Pacific Ocean, you might suddenly 'lose' a day. But go west, and you can gain one back. How is that possible without a time machine?