What I've Learned

I want to ask you and Julius Caesar a question. How many days are there in a year?

If you said 365.25, you and Julius are darn close. It actually takes the earth 365.242199 days – which is to say 365 days, 5 hours, 48 minutes, 46 seconds – to circle the sun.

During his reign, Caesar declared – when you are emperor, you can declare things – that instead of the old 365-day calendar, the Roman empire would go with a 365.25 day calendar. The quarter days would be made up for by adding an extra day, a leap day, to the calendar every four years.

Good idea. However, the difference between .25 of a day and .242199 of a day comes to around 11 minutes. This added up over time. By the 1500s, the calendar was out of sync with the seasons by about 10 days. That is to say, January 1st was arriving 10 days later in the earth's orbit than it did in Caesar's time.

What to do, what to do.

Aloysius Lilius, a physician from Naples, suggested a fix. Shift the calendar back 10 days to get January 1st where it was supposed to be and stop having so many leap years. Under Lilius's plan, instead of having 100 leap years every 400 years, there would only be 97.

Here's how. Every year divisible by 4 is a leap year. However, every year divisible by 100 is not a leap year, unless it is also divisible by 400.

The year 1700 would normally be a leap year, but because it can be divided evenly by 100, it's not.

The year 1600 is a leap year. It can be divided evenly by 100, but it can also be divided evenly by 400.

Hence, 1700, 1800, 1900, 2100, and 2200 are not leap years. But 1600, 2000, and 2400 are.

Under this plan, the calendar would stay so nearly in sync with the earth's trip around the sun, that it would take 3,300 years for it to be off by a single day.

In 1582, Pope Gregory XIII adopted this plan. Ten days were dropped (the 4th of October that year was followed by the 15th), and from then on, the reformed calendar was used. The result is called the Gregorian Calendar, which is the one we use today.

This change was all well and good for Catholic countries. Protestant countries, however, were reluctant to get on board, some waiting centuries to adopt the new system. Remember, changing over required the dropping of 10 days (or more, depending on what century it was) from the calendar.

Things were particularly whacky in Germany, which had some Catholic and some Protestant states. Catholic states made the change on various dates from 1583 to 1585. Prussia switched over in 1610. Protestant states, not until 1700.

Here in the U.S., things were just as crazy. Along the Eastern seaboard, states changed when Great Britain did, in 1752.

In areas with strong French influence, the change came much earlier, since France had switched clear back in 1582. The same is true of areas with heavy Spanish influence, Spain having also changed in 1582.

The northern Pacific area – Washington, Oregon – changed with Britain in 1752.

Alaska changed in 1867, when it became part of the USA.

Some countries, such as Albania, Bulgaria, Estonia, Romania, Russia, and China, didn't adopt the Gregorian calendar until the early 1900s.

It has been suggested that to keep our calendar from getting out of sync a day every 3,300 years, a new rule should be added, dropping a leap year every 4,000 years.

I like things to be tidy, so I'm in favor of it.