The Universe of Discourse

Tue, 17 Jan 2006

Thanks to the wonders of the Internet, the text of the British Calendar Act of 1751 is available. (Should you read the Act, it may be helpful to know that the obscure word "supputation" just means "calculation".) This is the act that adjusted the calendar from Julian to Gregorian and fixed the 11-day discrepancy that had accumulated since the Nicean Council in 325 CE, by deleting September 3-13, so that the month of September 1752 had only 19 days:

 September 1752 Sun Mon Tue Wed Thu Fri Sat 1 2 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Why September 3-13? I don't know, although I would love to find out. There are at least two questions here: Why start on the third of the month? Clearly you don't want to delete either the first or the last day of the month, because all sorts of things are scheduled to occur on those days, and deleting them would cause even more confusion than would deleting the middle days. But why not delete the second through the twelfth?

And why September? Had I been writing the Act, I think I would have preferred to delete a chunk of February; nobody likes February anyway.

Anyway, the effect of this was to make the year 1752 only 355 days long, instead of the usual 366.

I hadn't remembered, however, that this act was also the one that moved the beginning of the year from 25 March to 1 January. Since 1752 was the first civil year to begin on 1 January, that meant that 1751 was only 282 days long, running from 25 March through 31 December. I used to think that the authors of the Unix cal program were very clever for getting September 1752 correct:

        % cal 1752

1752

January               February                 March
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2  3  4                      1    1  2  3  4  5  6  7
5  6  7  8  9 10 11    2  3  4  5  6  7  8    8  9 10 11 12 13 14
12 13 14 15 16 17 18    9 10 11 12 13 14 15   15 16 17 18 19 20 21
19 20 21 22 23 24 25   16 17 18 19 20 21 22   22 23 24 25 26 27 28
26 27 28 29 30 31      23 24 25 26 27 28 29   29 30 31

April                   May                   June
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2  3  4                   1  2       1  2  3  4  5  6
5  6  7  8  9 10 11    3  4  5  6  7  8  9    7  8  9 10 11 12 13
12 13 14 15 16 17 18   10 11 12 13 14 15 16   14 15 16 17 18 19 20
19 20 21 22 23 24 25   17 18 19 20 21 22 23   21 22 23 24 25 26 27
26 27 28 29 30         24 25 26 27 28 29 30   28 29 30
31
July                  August                September
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2  3  4                      1          1  2 14 15 16
5  6  7  8  9 10 11    2  3  4  5  6  7  8   17 18 19 20 21 22 23
12 13 14 15 16 17 18    9 10 11 12 13 14 15   24 25 26 27 28 29 30
19 20 21 22 23 24 25   16 17 18 19 20 21 22
26 27 28 29 30 31      23 24 25 26 27 28 29
30 31
October               November               December
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2  3  4  5  6  7             1  2  3  4                   1  2
8  9 10 11 12 13 14    5  6  7  8  9 10 11    3  4  5  6  7  8  9
15 16 17 18 19 20 21   12 13 14 15 16 17 18   10 11 12 13 14 15 16
22 23 24 25 26 27 28   19 20 21 22 23 24 25   17 18 19 20 21 22 23
29 30 31               26 27 28 29 30         24 25 26 27 28 29 30
31


But now I realize that they weren't clever enough to get 1751 right too:

        % cal 1751
1751

January               February                 March
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2  3  4  5                   1  2                   1  2
6  7  8  9 10 11 12    3  4  5  6  7  8  9    3  4  5  6  7  8  9
13 14 15 16 17 18 19   10 11 12 13 14 15 16   10 11 12 13 14 15 16
20 21 22 23 24 25 26   17 18 19 20 21 22 23   17 18 19 20 21 22 23
27 28 29 30 31         24 25 26 27 28         24 25 26 27 28 29 30
31
April                   May                   June
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2  3  4  5  6             1  2  3  4                      1
7  8  9 10 11 12 13    5  6  7  8  9 10 11    2  3  4  5  6  7  8
14 15 16 17 18 19 20   12 13 14 15 16 17 18    9 10 11 12 13 14 15
21 22 23 24 25 26 27   19 20 21 22 23 24 25   16 17 18 19 20 21 22
28 29 30               26 27 28 29 30 31      23 24 25 26 27 28 29
30
July                  August                September
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2  3  4  5  6                1  2  3    1  2  3  4  5  6  7
7  8  9 10 11 12 13    4  5  6  7  8  9 10    8  9 10 11 12 13 14
14 15 16 17 18 19 20   11 12 13 14 15 16 17   15 16 17 18 19 20 21
21 22 23 24 25 26 27   18 19 20 21 22 23 24   22 23 24 25 26 27 28
28 29 30 31            25 26 27 28 29 30 31   29 30

October               November               December
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2  3  4  5                   1  2    1  2  3  4  5  6  7
6  7  8  9 10 11 12    3  4  5  6  7  8  9    8  9 10 11 12 13 14
13 14 15 16 17 18 19   10 11 12 13 14 15 16   15 16 17 18 19 20 21
20 21 22 23 24 25 26   17 18 19 20 21 22 23   22 23 24 25 26 27 28
27 28 29 30 31         24 25 26 27 28 29 30   29 30 31


This is quite wrong, since 1751 started on March 25, and there was no such thing as January 1751 or February 1751.

When you excise eleven days from the calendar, you have a lot of puzzles. For any event that was previously scheduled to occur on or after 14 September, 1752, you now need to ask the question: should you leave its nominal date unchanged, so that the event actually occurs 11 days sooner than it would have, or do you advance its nominal date 11 days forward? The Calendar Act deals with this in some detail. Certain court dates and ecclesiastical feasts, including corporate elections, are moved forward by 11 real days, so that their nominal dates remain the same; other events are adjusted so that the occur at the same real times as they would have without the tamperings of the calendar act. Private functions are not addressed; I suppose the details were left up to the convenience of the participants.

Historians of that period have to suffer all sorts of annoyances in dealing with the dates, since, for example, you find English accounts of the Battle of Gravelines occurring on 28 July, but Spanish accounts that their Armada wasn't even in sight of Cornwall until 29 July. Sometimes the histories will use a notation like "11/21 July" to mean that it was the day known as 11 July in England and 21 July in Spain. I find this clear, but the historians mostly seem to hate this notation. ("Fractions! If I wanted to deal in fractions, I would have become a grocer, not a historian!")

You sometimes hear that there were riots by tenants, angry to be paying a full month's rent for only 19 days of tenancy in September 1752. I think this is a myth. The act says quite clearly:

. . . nothing in this present Act contained shall extend, or be construed to extend, to accelerate or anticipate the Time of Payment of any Rent or Rents, Annuity or Annuities, or Sum or Sums of Money whatsoever. . . or the Time of doing any Matter or Thing directed or required by any such Act or Acts of Parliament to be done in relation thereto; or to accelerate the Payment of, or increase the Interest of, any such Sum of Money which shall become payable as aforesaid; or to accelerate the Time of the Delivery of any Goods, Chattles, Wares, Merchandize or other Things whatsoever . . .

It goes on in that vein for quite a while, and in particular, it says that "all and every such Rent and Rents. . . shall remain and continue to be due and payable; at and upon the same respective natural Days and Times, as the same should and ought to have been payable or made, or would have happened, in case this Act had not been made. . . ". It also specifies that interest payments are to be reckoned according to the natural number of days elapsed, not according to the calendar dates. There is also a special clause asserting that no person shall be deemed to have reached the age of twenty-one years until they are actually twenty-one years old, calendrical trickery notwithstanding.

I first brought this up in connection with Benjamin Franklin's 300th birthday, saying that although Franklin had been born on 6 January, 1706, his birthday had been moved up 11 days by the Act. But things seem less clear to me now that I have reread the act. I thought there was a clause that specifically moved birthdays forward, but there isn't. There is the clause that says that Franklin cannot be said to be 300 years old until 17 January, and it also says that dates of delivery of merchandise should remain on the same real days. If you had contracted for flowers and cake to be delivered to a birthday party to be held on 6 January 2006, the date of delivery is advanced so that the florist and the baker have the same real amount of time to make delivery, and are now required to deliver on 17 January 2006.

But there is the additional confusion I had forgotten, which is that Franklin was born on 6 January 1706, and there was no 6 January 1751. What would have been 6 January 1751 was renominated to be 6 January 1752 instead, and then the old 6 January 1752 was renominated as 17 January 1753.

To make the problem more explicit, consider John Smith, born 1 January 1750. The previous day was 31 December 1750, not 1749, because 1749 ended nine months earlier, on March 24. Similarly, 1751 will not begin until 25 March, when John is 84 days old. 1751 is an oddity, and ends on December 31, when John is 364 days old. The following day is 1 January 1752, and John is now one year old. Did you catch that? John was born on 1 January 1750, but he is one year old on 1 January 1752. Similarly, he is two years old on 1 January 1753.

The same thing happens with Benjamin Franklin. Franklin was born on 6 January 1706, so he will be 300 years old (that is, 365 × 300 + 73 = 109573 days old) on 17 January 2007.

So I conclude that the cake and flowers for Franklin's 300th birthday celebration are being delivered a year early!