Walking in the Valley A weekly column for those who live and walk in Silicon Valley by Barbara Dahlgren

The “True” Origin of Leap Year Column for the week of Feb 22-28, 2004

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"Thirty days has September, April, June, and November. All the rest have 31 except for February....yada, yada, yada.” I never could remember the last part of that poem. All I knew was February didn’t have 30 or 31 days. It has 28 unless it’s a leap year. Then it has 29. “Why is that?” you might ask.

Well, to find out we probably should look at origins of our calendar. Calendars are fascinating subjects. Just about every culture has had its own calendar. There is the Jewish, Gregorian, Islamic, French Revolutionary, Babylonian, Chinese, Aztec, Indian calendars and the list goes on and on. Calendars are not at all complicated. For example....

Ancient Greeks used the moon to come up with a lunar calendar. Greek philosopher, Meton, discovered 235 lunar months made around 19 solar years. Based on a 12-month year, every few years an additional lunar month needed to be inserted (in year 3, 5, 8, 11, 13, and 19 of the cycle). However this system wasn’t very popular. Although some religions use a lunar based calendar to calculate their holidays/holy days. We don’t use this calendar today except that when we celebrate Easter is based on the moon and Sunday and some other stuff. That’s why it’s on a different day every year.

Ancient Egyptians started numbering years when the star Sirius coincided with the Sun. It was the first solar calendar and had 365 days, divided into twelve 30-day months with a five-day festival at the end of the year. It became the standard used during the Middle Ages and by Copernicus. But of course this is not the one we use today, either. That 5 day festival thing at the end of each year could be a little tricky for some.

Roman calendars had 10 months totaling 304 days in a year, which was followed by an undetermined period of time known as winter. The calendar year would start again with the vernal equinox. Eventually some king added a couple of extra months which increased the year to a firm 354 or 355 days give or take a few days. It was considered a royal mess so in 46 B.C. Julius Caesar reformed it, adding a few days here and there to come up with three years of 365 days followed by a 366-day year called leap year. But leap years only occurred in years that were divisible by four. Unfortunately some helpful priests had been adding leap years every three years instead of 4. Then it was found that 10 days were missing somewhere so Pope Gregory XIII just omitted 10 days, making the day after October 4, 1582 to be October 15, 1582 inventing the Gregorian calendar. Presto-chango we had an easy to understand calendar that most of the world eventually adopted.

So now we have a 12-month calendar year adopted from the Roman/Gregorian model. Each month is named after Roman gods/goddesses, leaders, or the Latin word for a number. That’s why today we have months that coincide with the Latin roots for number 7 (September), 8 (October), 9 (November), and 10 (December) carrying over from the time when the Romans had a 10 month calendar. But of course these are the 9th, 10th, 11th, and 12th months of the year, now, which is not confusing at all if you don’t know any Latin roots.

“Why do we need a leap year?” you might ask. Well, it takes 365.2422 days for the earth to orbit the sun. We have an extra .2422-day, which is about 6 hours each year. That can really add up over a period of time so we try to even it out by adding leap years approximately every four year. And we use these simple rules to calculate when a leap year should be added:

1. Every year divisible by 4 is a leap year
2. But every year divisible by 100 is NOT a leap year
3. Unless the year is also divisible by 400, then it is still a leap year.

You see, it is all so very easy.

Is this the way God created it? One wonders if there isn’t some hidden trick that God has never revealed to us. After all, He made the sun, moon, and stars in their orbits. (Psalm 8:2-4) Or at creation did He just think, “I’ll do it this way. It will drive them nuts! They’ll leap around like a bunch of frogs trying to figure it out!” That may be how we really got the term “leap year.” Who says God doesn’t have a sense of humor?

Be sure to visit this page every week to read the next edition of Walking in the Valley. You can write to the author at bdahlgren@wcgsouthbay.org.