The Great Calendar Glitch of 1582, Explained

No, your iPhone’s calendar isn’t broken… it’s just showing one of the weirdest quirks in modern history: the Great Calendar Glitch of 1582.

Here’s the deal. Scroll back to October 1582… notice anything different? The dates jump straight from October 4 to October 15, skipping 10 days. If you’re asking yourself why, it’s because you’re actually seeing the Gregorian calendar reform in action.

So, what happened?

Before 1582, most of Europe used the Julian calendar, which had been introduced by Julius Caesar way back in 45 BCE. Problem was, it miscalculated the solar year by about 11 minutes. That tiny error added up over centuries, slowly shifting the calendar out of sync with the seasons. Religious holidays like Easter were drifting farther and farther away from the spring equinox.

To fix it, Pope Gregory XIII introduced the Gregorian calendar, which corrected the error by tweaking the leap year rules and, yes, deleting 10 days (which became 11 in some places due to accumulated differences). So when the change took effect in parts of Europe, the calendar literally jumped overnight from October 4 to October 15 in 1582. Those in-between days? They just… never happened.

Not everyone switched right away

Catholic countries like Italy, Spain, and Portugal made the switch immediately. Protestant and Orthodox countries, however, took their sweet time. England and its colonies didn’t adopt the Gregorian calendar until 1752 — by then, they had to drop 11 days instead of 10. Russia didn’t switch until 1918.

Alaska lost 11 days in 1867?

Alaska was owned by Russia until 1867. And they were still on the Julian calendar when they sold the land to the U.S. So, Alaska had to skip ahead 11 days overnight, and then they also had to repeat the same day again when the International Date Line was redrawn from the eastern border of Alaska to the western border. (Although it’s cold and dark there, so maybe they didn’t mind.)

A lot of people were not happy about it

In some places, people thought they were being robbed of days of their lives.

So yeah, your phone’s calendar is giving you a peek into one of the most quietly chaotic timekeeping changes in history. And if you were planning a birthday party for October 10, 1582… bad news. That day literally didn’t exist.