Once every few years, the world's timekeepers secretly add an extra second to the clock — and every time they do, the internet quietly has a small crisis. From Reddit going dark to a $350 million stock trading meltdown to a GPS glitch that nearly grounded planes, this is the story of why keeping computers synchronized with Earth's slightly-wobbly rotation is a genuinely unsolved problem. It turns out 'what time is it, exactly?' is one of the hardest questions in tech.