# Does 2011 Start a New Decade?

December 31, 2010
• Comment (23)

When the clock flips tonight will 2011 start a new decade or merely be the second year of the ’10s? As I wrote here and here, I maintain the former: “since our calendar goes from 1BC to 1AD, without a year zero, this is not technically the last year of the decade.”

When I made that argument a year ago, a reader responded with an interesting argument. Kevin S. of Ohio wrote:

I have to disagree that 2009 wasn't the last year of the decade. Unlike centuries and millennia, we don't number decades sequentially. We call our decades the 1980s, the 1990s, etc. While we call this century "the 21st Century," we know we won't call the past decade (even though its name is still up in the air) "the 201st Decade." Therefore, a strong case can be made that 2009 was the last year of the decade, since it was the last "200X" year. Granted, this causes some problems with the first decade AD, but nobody ever bothers with that period enough to want to give it a name.

I don’t think I agree, but it’s an interesting point.

Quoting Quentin

"This means- Pat- that on the 10th birthday that child has already lived one full decade. That means also -Pat- that on that very 10th birthday the child enters it's second decade".

And that very day after his 10th birthday would be the equivalent of year 11, or 1921 or 2011.

The first mistake made by those who argue that the decade begins at one and not zero is the erroneous assumption that there ever was a year one AD. There wasn't- it is simply a mathematical extrapolation (and one that contains many errors)

The Anno Domini numbering system was invented by the Roman monk Dionysius Exiguus in (what would become) the year 525 AD. At that time the Roman calendar changed with each emperor (for instance "the 3rd year of Romulus", or "the 9th year of Cicero" etc. etc.) A consecutive calendar dating back to time immemorial would have been considered ludicrous and meaningless. The AD numbering system did not come into common use until the reign of Charlemagne. (742-814)

The second mistake is assuming that Christ was born in the year "1 AD" Scholars disagree on whether Dionysius intended the birth of Christ to be 1AD or 1BC. If he meant 1BC then of course 1BC becomes in essence year zero. There is a very good reason to believe that Christ was born in 1BC and that is King Herod is dead by 1AD. (using the Dionysian calculation)

We cannot use the year 1AD as a starting point because not only is it theoretical and erroneous, but our calendar has been adjusted many times since then. And we here United States have only had stable decades since 1752 when the last adjustment was made to the calendar we use.

You're right in that 9 x 365 is 3285. What you are neglecting or forgetting are the 365 days that occur before the year 1. By the time a child reaches age 1 he/she is 365 days old. A baby does not start at year one- it takes 365 days to reach year one. The child actually begins life one year before year 1. So the day before the 10th birthday that child is 3650 days old (more or less because in any give 10 years there are least 2 leap years) This means- Pat- that on the 10th birthday that child has already lived one full decade. That means also -Pat- that on that very 10th birthday the child enters it's second decade.

(birth to age 1) 365 days,

(1-2) 365 days,

(2-3) 365 days,

(3-4) 356 days,

(4-5) 356 days,

(5-6) 365 days,

(6-7) 365 days,

(7-8) 365 days,

(8-9) 365 days

(and finally the year 9- 365 days)

add that up Pat (or let me help- it's 3650 days)

On the day of the child's 10th birthday (10th Pat- 10th) the child has surpassed a decade and is in decade 2.

Red faced Pat?

#### Robert Schlesinger

Robert Schlesinger is managing editor for opinion at U.S. News and World Report, overseeing all opinion editorial content. He is the author of "White House Ghosts: Presidents and Their Speechwriters." E-mail him at rschlesinger@usnews.com. Follow him on Twitter: @rschles.