The date should always be given in Arabic figures; and if there is any peculiarity in the form of the date as it occurs in the book, it should be added between brackets. The day of the month, when it is given in the colophon, should always be put down in the description, as it is often of great importance. In countries where the new year began in March we are apt to get confused with the dates, and forget, for example, that the 20th of January 1490 is later than the 20th of December 1490.
The beginning of the year varied in different countries, and often in different towns. The four most usual times for its commencement were: Christmas Day (December 25), the day of the Circumcision (January 1), the day of the Conception (March 25), and the day of the Resurrection (Easter Day). The 25th of March was, on the whole, most common; but in dating any book exactly, the rule for the particular town where it was printed should be ascertained.
An approximate date should always be supplied to the description of an undated book; but this date should not be a mere haphazard conjecture, but should be determined by an examination of the characteristics of the book, and comparison with dated books from the same press, so that the date that is ascribed is merely another expression for the characteristics noticed in the book. It is only after careful study that accurate dates can be ascribed to books of a particular press, and monographs on particular printers must be consulted when it is possible.
On the question of sizes there seem to be many opinions. There was originally no doubt on the subject, and there is no reason for any doubt now.
There are two opposing elements at work, size and form. Originally, when all paper was handmade, and did not vary very much in measurement, books were spoken of as folio, quarto, octavo, etc., according to the folding of the sheet; and these terms apply to the folding of the sheet. In the present century, when paper is made by machinery, and made to any size, the folding cannot be taken as a criterion, and the various sizes are determined by measurement, the old terms, applicable only to the size by folding, being retained. What has evidently led to all this confusion is the application of the same terms to two different things.