But in reducing a Roman date to a date of February in leap-year, for the first twenty-four days, proceed according to the preceding rule as if the month had only twenty-eight days, and to obtain the proper expression for the remaining five days, regard the month as having twenty-nine days, taking the Roman date from 31 instead of 30. Thus 31 - 6 = 25, while 30 -6 = 24; the former corresponding with sexto calendas, the latter with bis-sexto calendas of the Julian calendar. By referring to the table on the 35th page, one may easily learn how to find the English expression for any Latin date, or the Latin expression for any English date.
It has already been stated that in January the Nones fall on the 5th, and the Ides on the 13th, January then having thirty one days, the number from which to subtract the Roman date to obtain the corresponding day of the month is, for Nones, 5 + 1 = 6; for Ides, 13 + 1 = 14; for Calends, 31 + 2 = 33. Hence the first column in the table under January are the numbers 6, 14 and 33. February is the same as January for Nones and Ides. For Calends in leap-year, for the first 24 days, it is 28 + 2 = 30; for the remaining 5 days it is 29 + 2 = 31. Hence for the first column under February are the numbers 6, 14, 30 and 31. March is the same as January, except that the Nones fall on the 7th and the Ides on the 15th, consequently we have for Nones, 7 + 1 = 8, and for Ides, 15 + 1 = 16; hence, for the first column under March we have the numbers 8, 16, and 33.
In the table the three months are taken to illustrate how easily the change may be made from Roman to English, or from English to Roman date. A complete calendar for 1892, both in Roman and English, which will be very convenient for reference, may be found on the four following pages.
The first seven letters of the alphabet, used to represent the days of the week, are placed in the calendar beside the days of the week. The letter that represents Sunday is called the dominical or Sunday letter. The letter that represents the first Sunday in any given year represents all the Sundays in that year, unless it be leap-year, when two Sunday letters are used. The first represents all the Sundays in January and February, while the letter that precedes it represents all the Sundays for the rest of the year.