An attempt to explain this has been made by a certain magazine, which seriously informs its readers that "the secret 'of the how' is neither a remarkable 'gift,' nor surprising mental or mathematical ability, as is usually supposed.
"The performer holds concealed in his hands tablets on which formulas are engraved, or they may be written on his shirt cuffs. He raises a hand to his head, as though meditating, and can thus, unnoticed, glance over the tabulated formulas. Or he stands before the audience with folded arms, coat sleeves drawn well back, which gives ample opportunity for a quick yet careful glance at the unpretending cuffs; but instead of gazing at the floor in deep thought, as is commonly supposed, he is studying the formula dexterously concealed from the audience."
All this sounds very learned, but as there are no less than six tables given as absolutely necessary for the accomplishment of the trick—one of them of thirty-one lines and eight columns—the performer who should attempt it on that plan would require, instead of eyes, what Sam Weller calls "a pair o' patent double million magnifyin' gas microscopes of hextra power."
I know of three different short methods of arriving at this calculation, by which any one with a fair memory and an elementary knowledge of mental arithmetic can answer almost instantly the question, On what day of the week does a certain date fall? The easiest and best of these is as follows: First memorize the following couplet:
| 1 | 2 | 3 | 4 | 5 | 6 |
| Time | Flies | Fast | Men | Wisely | Say; |
| (Tuesday) | (Friday) | (Friday) | (Monday) | (Wednesday) | (Saturday) |
| 7 | 8 | 9 | 10 | 11 | 12 |
| Many | Think, | Alas, | Time's | Fooled | Away. |
| (Monday) | (Thursday) | (Sunday) | (Tuesday) | (Friday) | (Sunday) |
These twelve words stand for the twelve months of the year, while their initial letter or letters represent the days of the week, as shown by the lines in parentheses, Sunday being represented by A.
To find out the day of the week on which a certain date falls in a leap-year, take half of the last two figures of the given year, divide by 7, and the remainder gives the date. For example, 1880: The half is 40; divided by 7, equals 5, with 5 remaining. Therefore, March 5th would fall on a Friday; June 5th on a Saturday; September 5th on a Sunday; and so on. To get the other dates is a matter of simple addition.
According to this, January 5th would be Tuesday, and February 5th Friday, but in leap-year the remainder must be increased one; therefore January 6th would be Tuesday, and February 6th Friday.
In non-leap-years, take the previous leap-year, and subtract one for each year past that leap-year. For example: Let us suppose that some one asks on what day of the week July 29, 1895, fell. The previous leap-year was 1892; the half of 92 equals 46; subtract one for each year past—i.e., 3—which would be 43; this, divided by 7, would leave a remainder of 1. So that July 1st fell on a Monday, and adding 28 days, four full weeks, gives us Monday, which your calendar will show you is right.
If in dividing the last two numbers of the given year there should be no remainder, the date is 7.