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2010: A New Decade?

New Year's Eve, London
More or Less
Friday, 8 January 2010
BBC Radio 4, 1330 GMT

Last week, Jonathan Betts of the Royal Observatory in Greenwich debated with Paul Lewis of Money Box over the question of whether we had entered a new decade or not.

Here is Jonathan's response to the many emails we have received on the topic:

Paul Lewis and I agree that a decade is any period of 10 years, and anyone is free to call any such period 'a decade', whenever it begins or ends.

Thus, for example, the term "1980s" suggests a decade including all the years with the number eight as its third digit (i.e. the years 1980 to 1989 inclusive) and one is perfectly entitled to call that "...the decade that was the 1980s".

However, that was not the issue under discussion on More or Less.

The question concerned Paul Lewis' remark on Money Box, that the first decade of the 21st Century ended at close of play on 31 December, 2009.

The remark was questioned by some listeners and I was asked for the 'official' answer which is that, mathematically and logically, his statement was simply not true.

Setting aside the pedantry and the irritating logic, then of course people can go with what makes them feel more comfortable, and what they see as significant.

Spanish revellers at New Year
Did they celebrate too soon?
There is no law against considering the beginning of the numerically-attractive year 2000 as being the start of a new millennium.

Similarly, we can refuse to accept that the '1980s' were in fact the ninth decade of the 20th century, or that that decade officially ends at the end of the year 1990 (both literally correct).

All this we can do, and most people are happy to agree or disagree with such generalities.

But, if one is asked whether, strictly speaking, those statements are mathematically correct, there is only one answer: NO.

One must also set aside the question of whether the retrospective calculations were correct for the birth of Christ, when the calendar was created in the first place.

This is an entirely separate question.

It may well be that the moment chosen was incorrect, and that the birth of Christ was some years earlier, but that does not alter the logic of the numbering sequence which we use to reckon when the end of 10 years, a century or a millennium or two has elapsed in the series of years we are using.

The misunderstanding seems to have arisen by people confusing numbering with counting.

Fireworks, Berlin
The debate caused fireworks on last week's programme
Numbering in the Julian/Gregorian calendar allocates a number to whole years, beginning with year one.

We tend to mark the year's number when it arrives, i.e. at the beginning of the year, and use that number during the whole period of 12 months.

Counting, as for example we do when we mark our birthdays, occurs at the moment when a given year is completed.

It seems it would satisfy many people if we were to adopt that means of marking the calendar year, and note the number at the completion of a year rather than at its beginning, but currently that is simply not the way it is.


The BBC Radio 4 More or Less programme referred to above was broadcast on Friday, 8 December 2010 at 1330 GMT and was repeated on Sunday, 10 December at 2000 GMT.

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