Monday, December 07, 2009

decade's end

remember ten years ago, in late 1999, when everyone was planning some big "turn of the century/millennium" celebration? inevitably some smart alec would come along and say "december 31, 1999 isn't really the turn of the century, the century (and/or millennium) doesn't begin until january 1, 2001." the annoying thing about those smart alecs is that they were right. it didn't make them less annoying, but it is true that the 21st century and 3rd millennium technically began on the night that 2000 became 2001, and not the night when 1999 turned to 2000.

recently i've noticed that the smart alec is back, with a new but similar point. just this morning i was listening to the radio and one called in. they were talking about the end of the current "aught" decade. the smart alec's new point is that the "aught" decade doesn't really end later this month. he said that it really ends one year from now, on december 31, 2010.

while he may have been right in 1999, this time the smart alec is wrong.

if i may attempt to out-smart the smart alec: the reason why the smart alec's trick works when he was talking about the turn of the century is because usually when we speak about centuries we describe them with ordinal numbers, e.g. "seventh century", "eighteenth century", "twentieth century." when you use ordinal numbers you're suggesting a count from some beginning point. it's not just #21, this is the 21st century since we started counting A.D.

if we're counting a century, we're really counting a block of 100 years. the first century is the first hundred years, which is year 1 through 100. the second century is the second hundred years, the year 101 through 200. and so on. the pattern that emerges is that only the last year does the number of the century correspond to the beginning of the written out year. which can be confusing. for the first 99 years of each ordinal century seems to be ahead of itself.

however, there are times that people use cardinal numbers to talk about centuries. for example, sometimes they say stuff like: "the eighteen-hundreds." "the eighteen hundreds" (unlike "the nineteenth century") is referencing the century by citing the beginning digits of the written date. it's not counting the centuries from the beginning, it's referring to the digits used to write the year. it's a different system for referring to centuries, a system that uses the cardinal numbers from our date notation system, not ordinal numbers.

because that system, the "eighteen hundreds" system, doesn't use cardinal numbers, it doesn't produce the same one-off effect you get a cardinal system like the "nineteenth century". the "eighteen hundreds" refers to every four digit year that starts with an "18". that is, from 1800 through 1899. note that 1800 is in the eighteen hundreds even though it's not in the nineteenth century, even though all the other years in the eighteen hundreds are.

essentially we have two different systems for talking about centuries. the most common when we speak is the ordinal system ("twenty-first century"). but we usually think about dates in terms of a cardinal number ("2000"). it's the switch between the two that make this so confusing. the two different systems treat the dates ending with double-zeros differently. under one system they're in the same century of the preceding year and under the other they're in the same century of the succeeding year.

so that's why the smart alec was right in 1999. why isn't he right anymore?

it's because when we talk about decades we only use cardinal numbers. this decade is the "aughts" or the "zeros", whatever you want to call it. but no one ever calls it the "first" (if we were counting from the beginning of the 21st century) or the "two-hundred and first" (if we were counting the decades from the beginning of the AD calendar). when we refer to decades we are not counting how many decades there have been since some starting point. instead we identify decades by referencing the cardinal number in the tens column in the written year.

thus, the "seventies" went from 1970 through 1979 and not from 1971 through 1980, because it refers to the dates with 70 in it. likewise, the "aughts" run from 2000 through 2009 because those are the years with a zero in the second to last digit when we write the date. when it comes to decades, there is no quirky effect as you get with the ordinal system of discussing centuries.

the smart alec was assuming that decades and centuries are conceptualized the same way. they are not. bad smart alec!