ELI5: Why are leap seconds being phased out of the world's official timekeeping?

Leap seconds are being phased out because they confuse the computers and networks that run our everyday world, causing technical glitches that can break modern services.

Imagine you are clapping your hands to a steady song. That is how atomic clocks work—they keep time with super-steady, perfect ticks. Now imagine a friend is spinning around in a circle, and you want each clap to match their spins. That spinning friend is planet Earth.

The problem is that the Earth is a bit wobbly and slowly changes its spinning speed. Sometimes it gets a tiny bit tired and slows down. To keep our super-accurate atomic clocks matching the spinning Earth, timekeepers used to hit "pause" for just one tick. That extra tick is a leap second.

While an extra second sounds harmless, it causes big headaches in everyday life because modern technology relies on exact time:

• Travel and Navigation: Airplanes, trains, and GPS maps depend on computers that agree on the exact time down to the millisecond. If one system pauses for a leap second and another does not, navigation can get confused.
• Online Shopping and Banking: When you buy something online or swipe a credit card, the bank needs to know the exact order of transactions. A surprise second can cause the system to record payments twice or fail completely.
• Social Media and Streaming: Big internet websites have crashed in the past because their computer servers did not know how to handle the 61st second in a minute.

Scientists decided that in the near future, we will stop adding these single seconds. Instead, we will just let our clocks slowly drift a tiny bit away from the Earth's spin. It would take hundreds of years for that difference to equal even a single minute, which is something our computers can easily handle without crashing the apps, websites, and travel systems we use every day.