In modern times it is the universal practice to reckon dates by days and not by nights.  The word “day” is used in two different significations, being sometimes applied to the period of daylight and sometimes to the period of 24 hours, including both day and night; but in whichever of these senses the word day is employed, the term mid-day has one and the same signification, viz., the instant of noon or of the sun’s passage over the meridian.  In the present case, where we are concerned with mean time, mid-day means the instant of mean noon, or of the passage of the mean sun over the meridian.

Accordingly, the civil day, by which all the ordinary affairs of life are regulated, begins and ends at midnight, and has its middle or mid-day at noon.

It appears, then, most natural that the universal day should follow this example, and should begin and end at the instant of mean midnight on the initial meridian, and should have its middle at the instant of mean noon on the same meridian.

I fail, therefore, to see the force of the reasons which induced the Conference at Rome to recommend that the universal day should commence at noon on the initial meridian.

The only ground for making this recommendation is that astronomers, instead of adopting the use of the civil day, like the rest of the world, are accustomed to employ a so-called astronomical day, which begins at noon.  The advantage thus gained is that they avoid the necessity of changing the date in the course of the night, which is the time of their greatest activity; but this advantage is surely very small when compared with the inconvenience of having two conflicting methods of reckoning dates, and of being obliged to specify, in giving any date, which mode of reckoning is adopted.  If this diversity is to disappear, it is plain that it is the astronomers who will have to yield.  They are few in number compared with the rest of the world.  They are intelligent, and could make the required change without any difficulty, and with very slight or no inconvenience.

The requisite changes in the astronomical and nautical ephemerides would be easily made.  As these ephemerides are published several years in advance, there would be plenty of time for navigators to become familiar with the proposed change in time-reckoning before they were called upon to employ it in their calculations.

I believe that they would soon come to think it more convenient and natural to reckon according to civil time than according to the present astronomical time.  I am told that this practice is already universally adopted in keeping the log on board ship.  To avoid any chance of mistake, it should be prominently stated on each page of the ephemerides that mean time reckoned from mean midnight is kept throughout.

Whether or not astronomers agree to adopt the civil reckoning, I think we ought to adopt the instant of midnight on the initial meridian as the commencement of the universal day.