Another important point to notice is that, since it is the time of the equinox, there is no difference between “temporary” and “equal” hours.[450] Days and nights are of equal length; sunrise and sunset are nearly at 6 a.m. and 6 p.m., according to our modern method of reckoning.[451] In this way also, and without any sacrifice of astronomical accuracy, the poet has simplified his time references for his readers. ------------------------------------------------------------------------ [450] _Conv._ III. vi. 28-30. [451] On the day of the spring equinox the sun rises and sets a few minutes after six o’clock, because we set our clocks not by the real sun but the more convenient “mean sun.” ------------------------------------------------------------------------ We must observe, however, that the day is as uncertain as the year; for, although it is certainly near the equinox, “quelle stelle” may mean exactly the first point of Aries or only the constellation Aries in general. From this Canto alone, therefore, we cannot be sure of the exact date. From other allusions of various kinds, scattered throughout the _Divine Comedy_, we gather that Dante did intend a definite date to be understood, but unfortunately the data by which he means to fix it are themselves so ambiguous that commentators differ as to the day, the month, and the year. The question has so direct a bearing on Dante’s astronomy that we cannot shirk it; but for the present, leaving it aside, let us deal merely with the hour, which is distinctly stated from the first, and indicated in a number of passages so clearly that readers with an elementary knowledge of the apparent movements of the heavenly bodies can find little difficulty in following Virgil and Dante through their journey, seeing exactly how many days it required, and frequently at what hour of day or night they were in a particular spot. If my readers are not now in possession of this elementary knowledge, this book has been written in vain. I give below a list of all the hour-indications, astronomical and others, for the sake of clearness and completeness; but I omit for the present those that indicate only the date, and merely call the days the first, second, etc. These passages, though they are only to be understood in a popular sense, prove quite as clearly as the elaborate astronomical explanations in the _Convivio_ how deep an interest Dante always took in astronomy; and a study of them shows that he had carefully considered the positions of the heavenly bodies and their movements during the progress of the action in his poem. TIME REFERENCES IN THE DIVINE COMEDY Night. In the Forest. Moon full (see below, _Inf._ xx. 127-129, and _Purg._ xxiii. 118-121).