In 1582, Rome and Madrid did something that sounds like a printing error.

People went to bed on Thursday, October 4, and woke on Friday, October 15.

The sun rose on time. They slept their usual hours. Nobody aged ten days in one night.

Why were the dates gone?

The Julian year ran a little long. The spring equinox had drifted from March 21 to March 11, so Easter no longer fell in its place in the season.

Pope Gregory XIII issued the bull Inter gravissimas on February 24 that year.

Luigi Lilio, a Calabrian physician and astronomer, built the foundations.

Christopher Clavius, a German Jesuit mathematician, developed them further.

In Catholic lands the next day simply wore a new date. Ten calendar dates were missing.

The week continued normally, from Thursday to Friday.

Austria, Spain, Portugal, Italy, Poland, and Catholic Germany suddenly ran ten days ahead of the rest of the continent.

Protestants and the Orthodox refused an order from the pope.

They kept the old calendar for centuries.

Crossing a border often meant moving forward or backward through the dates.

Life did not lose a single hour.
The calendar lost only paper.