[LEAPSECS] LEAPSECS Digest, Vol 88, Issue 31

[Richard Clark]

General agreement for December 31 as the end of any year, century, etc is
fairly recent.

While January 1 was used to mark the start of a year in some places
so were March 1, March 25, September 1, December 25, and possibly
others. The switch to January 1 for year numbering came at various
times in various regions. Old and new style forms for document dating
often coexisted for decades. The switchover was distinct from the
switch from Julian to Gregorian but generally happened over the same
few century span of 1500s - 1700s that most countries converted. The
switch to using Jaunary 1 for the new year waw usually prior to the
adoption of the Gregorian calendar.

And as for counting-- it's not always in the realm of mathematicians.
When you enter a building on ground level and you go to a room on the
1st floor do you expect to use the stairs or elevator? The answer depends
on wheather you are in Europe or the US (or on the campus of the University
of Arizona).

I've always liked the view that the first century spanned the years
1-99. All subsequent centuries have spanned the years NN00 - NN99. It
makes a lot more sense than some of the stuff out there. The current
year numbering system came into use several centuries after the first
so 'the 1st Century' was not even in use during the 1st, 2nd, or 3rd
centuries. 2000 years ago seems a good place to bury the problem.

Richard Clark
rclark at noao.edu

On Tue, 14 Jan 2014, Poul-Henning Kamp wrote:


> In message <000301cf117f$cb7b7be0$627273a0$@comcast.net>, "Gerard Ashton" write

> s:

>

>> no authority is in a position to demand that December

>> 31, 2000, be regarded as the last day of the 20th century.

>

> I do belive mathematicians have done a fair bit of work on counting,

> and that they are entitled to deference in this particular case.

>

> It follows rather trivially from the fact that there were no

> year zero, that the first century must contain the years [1...100] in

> order to be a century.

>

> Proof by induction will then lead you to the fact that century

> number N contains the years [N*100-99, N*100]

>

> Consequently the 20th century must be the years [1901...2000]

>

> Q.E.D.

>

> -- 

> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20

> phk at FreeBSD.ORG         | TCP/IP since RFC 956

> FreeBSD committer       | BSD since 4.3-tahoe

> Never attribute to malice what can adequately be explained by incompetence.

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