How Timezones Were Invented (And Why They Are a Mess)

Before the 19th century, every town set its clocks by the sun, meaning noon was when the sun was highest. This worked fine when travel took days, but railways made it a crisis: a train from London to Bristol would pass through towns each keeping slightly different time. In 1884, the International Meridian Conference in Washington DC established Greenwich as the prime meridian and divided the world into 24 hourly zones. The system was simple in theory but messy in practice. China uses a single timezone despite spanning five geographically. India uses a 30-minute offset. Nepal is 45 minutes ahead of UTC. The International Date Line zigzags to avoid splitting countries. Daylight saving time further complicates matters, with different countries starting and ending on different dates. The result is a system that works adequately but is full of edge cases that trip up even experienced developers.