• Day 18: DST and The Related Software Bugs

  This is one of two or three DST posts in the 30 Days of Time series. Today’s angle: the software bugs. Twice a year, in most of the developed world, the clocks jump forward in spring and back in fall. The hour that doesn’t exist in spring …

• Day 17 — Time Zones Are a Nightmare

  Yesterday I wrote about how 2026-05-24T14:30:00Z won the format wars. That Z at the end, it turns out, is quite important. It says Zulu, it says UTC, it says: I am refusing to participate in the nightmare that is Timezones. However, today …

• Day 16: How the World Agreed on a Date Format (Except the US)

  There is a war that has been quietly raging for about a century, and it is fought over six little characters. 05/06/26 In the United States, that is May 6, 2026. In most of Europe, it is June 5, 2026. In Japan, which uses a year-month-day …

• Day 15: The Man Who Synchronized the World

  David Mills, the father of internet time, wrote the protocol that synchronizes every computer on Earth. He did it as a professor at the University of Delaware, on a project he started in the early 1980s and never stopped working on. The …

• Day 14: The Bug That Didn't End the World, and the One That Still Might

  On December 31, 1999, a measurable percentage of the developed world stockpiled bottled water, withdrew cash from ATMs, and stayed up to see if the lights would go out at midnight. They didn’t. Planes did not fall from the sky. Power grids …

• Day 13: Unix Time, 1,780,620,532

  That’s roughly what time it is, right now, as I type this. Not 8:48 PM. Not “Thursday.” Not “June 4th, 2026.” None of those are what your computer thinks “now” is. To your laptop, your phone, your car’s infotainment system, the streaming …

• Day 12: Earth to Mars, Come In

  NASA’s Mars mission control runs on Mars time, not Earth time. For the first few months of every landed mission (Curiosity, Perseverance, Insight), the scientists shift their work schedules by 39 minutes every day. They go to sleep 39 …

• Day 11: What If We Put Clocks in Space?

  In 1977, three years before GPS launched, the engineers building the satellites had to make a decision. The clocks they were about to put in orbit were going to run faster than the clocks on the ground. By about 38 microseconds per day. …

• Day 10: The Zero Point

  Three epochs quietly run the world: The Unix epoch. Midnight, January 1, 1970. Almost every computer measures time as seconds since this instant. The GPS epoch. Midnight, January 6, 1980. Every GPS satellite, every navigation chip in every …

• Day 9: A Clock You Can Use to Measure a Mountain

  Yesterday I said cesium was about to be deposed. Today’s the deposition. The successor is the optical lattice clock. It is so precise that, it can detect the altitude difference between two desks in the same office. That last sentence …