Feb 28, 2020

From the Julian to the Gregorian Calendar: A Leap Up


Pope Gregory XIII, born Ugo Boncompagni,
head of the Catholic Church, 13 May 1572 to his death in 1585.

The date was October 4, 1582, and people in Europe went to bed that night knowing that when they woke up it would already be October 15. (Well, many people probably didn’t know that and when they woke up, they were very surprised to learn that their rent was already due again.)

How did this happen?


In 1582 the Gregorian calendar was introduced in much of Europe—the calendar that is today used in much of the world.

The calendar was named after Pope Gregory XIII, who introduced it to correct a major problem in the Julian calendar. That calendar had been used since the Roman emperor Julius Caesar introduced it in the year 708.

One problem with the Julian calendar was it did not have correct leap years, and days were at times added every three years, instead of every four.

Pope Gregory’s new calendar shortened the average year by 0.0075 days to make it 365.2425 days long. In 1582, there was an estimated ten days’ difference between the calendar and reality, so in October of that year, people in Europe lost ten calendar days.

(Netflix did not offer refunds or discounts.)

The Julian calendar is still used in parts of the Eastern Orthodox Church, the major church for Russia and much of Eastern Europe.

Before Julius Caesar, the Roman calendar had 355 days, and in some years a 27- or 28-day month was added between February and March. But it was not systematic. It was up to Rome’s pontifices (Roman priests) to decide when to add a leap month.

Sometimes these priests were also politicians and added leap months for political reasons. Also, they sometimes decided very late (at the last minute), so the people of Rome didn’t know what the date was.

The final years before the Julian calendar were known by some people as “the years of confusion.”

So appreciate this extra day in the leap year 2020 as a day that helps us remember when to pay our bills. Thank Gregory!




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