CIIRONOLOGY is the science which treats of the measurement, denotation, and recording of time. That part of it which deals with the units of time, as defined by the revolutions of the heavens, is called Theoretical or Mathematical Chronology. The consideration of the methods, adopted by dif ferent nations, of reckoning the succession of these units, of dividing them into smaller, and grouping them into larger portions of time, and of giving names to these natural or conventional units, in order that each may have its own proper appellation, forms the subject of Technical or Applied Chronology. And when, by means of this nomenclature, the events of the nations are set forth in their due re lations of time, this (which, properly speaking, is a branch of history) is called Historical Chronology.
2. The date of an event is the name of the time of its occurrence, and to assign the date of a past event is to say haw long ago it took place. The reckoning in every case, ultimately and essentially, has its point of departure in the present instant, the now of the speaker. The savage has no other method of dating an event than to say that it oc curred so many days, or moons, or summers and winters ago; and a date expressed in terms of the most finished nomenclature of time resolves itself at last into the same procedure. For the statement, ' On such a day of a given month and year, in such an era or succession of years,' gives the measure of the time elapsed from the epoch or commencement of the era, reign, or other succession of years to the occurrence of the event, and assumes that it is known or ascertainable by what number of years, months, days, etc., that epoch precedes the present instant, or some other instant, the distance of which from the present is known. Otherwise, the date is only relative, not absolute.
3. For purposes of historical denotation, it mat ters not what method of dividing, arranging, and naming the portions of time be adopted, provided the method be constant, and the information cap able of rendering an answer to the question, How long ago ? or, which is essentially the same thing, How long before or since the epoch of the Chris tian or any other known era : the only difference being this, that a fixed instant of time is taken as the point of departure in place of the ever-shifting Now of the speaker (the is e of Herodotus, e.g., ii. 145,
which his reader has to fix as best he may). Thus, such a day, month, and year of the era of Nabon assar, or of the Hegira, can be rendered with ab solute precision in year B.C. or A. D. , and month and day of Julian or Gregorian Calendar, because in both eras, the epoch, the dimensions of the years, and the calendar arrangements, are absolutely known. It makes no difference whatever, that the Nabonassarian (or Egyptian vague) `year' consists only of 365 days, and the year of the Hegira only of 354 days, neither of them a true measure of the tropical year. In both eras, each day has its name and designation, which distinguishes it from all others, past, present, and to come, and this is all that is needed for purposes of chronology. The convenience of civilized life requires that our year' should be brought by well calculated intercalation as near as possible to the dimensions of the natural year ; but this is a consideration so perfectly dis tinct from the requirements of chronology, that if instead of the `year' as our larger unit of time, we chose to reckon by periods of any assignable number of days, say Soo or I000, with a calendar, which should give each of them a name, every pur pose of dating' would be attained.
4. Biblical Chronology. —If the chronology of the O. and N. T. is to be ascertained as a whole or in part, e.g., if we are to be enabled to ex press such statements as t sth year of Zedekiah, i4th of Hezekiah, 4th of Solomon, in equivalent terms of the era B.c., it is necessary, first, to col late all the cardinal notes of time contained in the record ; to ascertain their genuine form, import, and authority ; to obtain from them, thus digested, a continuous tract of time, with no gaps and no over lappings ; and, lastly, to refer this by means of proved synchronisms with other accredited history, to some fixed and known point of time. Until this is done, and so done that there remains nothing questionable or conjectural in the procedure, we have no de terminate chronology, and any dates we may assign are only approximate, and more or less hypothetical and precarious.