THE CALENDAR

Evening Post, Volume CXX, Issue 112, 7 November 1935, Page 11

THE CALENDAR

ALWAYS A PROBLEM

HUMAN INERTIA

IN WAY OF REFORM

"The whole history of the calendar emphasises human inertia and opposition to change in this time-table of life. We have a modern instance of this in daylight saving," declared Mr. John C. Begg, F.R.A.S., of Dunedin, retiring president of the New Zealand Astronomical Society, in an address upon' astronomy and the calendar to the annual meeting of the society last night. ' ' ' "Most of us, when hanging up our new calendar in January,". said Mr. Begg, "are content to take it lor granted as a kind of gift from the gods, the thought of questioning its veracity or perfection seldom or never occurring to us. ... Suggestions of alterations, in the calendar which we use have, however, not infrequently been made in late years, and it is quite conceivable that our complacency may be challenged in the future by legislative proposals involving changes. In any case, intelligent comprehension of the history and rationale of the present scheme is a pleasant cultural asset." The purposes served by the calendar were threefold, continued Mr. Begg. It provided a means of making definite appointments for ordinary social and business life and also for special national and religious celebrations and festivals, it served as a guide for seasonal work, notably in agriculture and horticulture, and it provided a frame of reference for records and predictions. The first arresting cyclic change which could not escape detection by the most primitive mind was the sequence of night and day caused by the rotation of the earth, and days and nights were therefore fundamental units of time. The next most obvious cyclic change in the sky was the recurring new and full moon which was the basis of the month. Y->t the importance of the annual round of seasons could not be left out of account, and so there were three distinct astronomical cycles, each with an important claim to consideration as the basis of time computation. The question arose: Which should be the fundamental unit? Or should we include them all? The latter course presented a central difficulty that had always perplexed the makers of calendars, arising from the fact that the periods \vere not commensurable as units; in other words, a year did not contain an equal number of days or of lunar periods. The weekly period had no foundation in astronomy or in Nature, but the number seven had a mystical significance among some.ancient peoples. THE GREAT PROBLEM. The division of the day into hours, minutes, and .seconds was purely arbitrary. The great historical problem had concerned the month and the day as component parts of the year, which actually consisted of rather Jess than 365 i aays,- while the month was rather more than 29J. days. The ancient Egyptians used a year of 12 months of 30 days each and added a complementary 5 days, making 365 in all. Their calendar possessed the distinction of being the only one until the time of the---Roman'- Julian reform, which yielded to the historian a definite result without the uncertainty of a possible capricious insertion of days and months. In the third century B.C. an attempt was made to add an extra day for leap year, but this was not accomplished before the reformed Roman calendar, and even then it was only slowly adopted generally. Remarkably accurate computations of the lunar period were made as early as the fourth century 8.C., but a small error in the length of the year ultimately led by accumulation to serious | d error in the seasonal dates, and the f< story of ancient calendar-making was largely one of recurring expedients for aligning the solar year with the f< moon periods. There was also much local variation of the time of com- n mencement of the year, and the inser- ? tion of months—intercalary months— *r was often haphazard,- the authorities who controlled the matter often doing ai so with an eye to political considera- s tions. under the. Roman calentfar, the foundation of our present scheme, it B. was also left to political .authority to correct the year by intercalation of w months or days, "but this was evident- ** ly neglected, for in the time of Julius ni Caesar the- correspondence with the seasons was months away from the di truth, and he rectified it by putting P' in two extra months in the year 46 T 8.C., which was called "a year of con- °' fusion." The extra' day for leap year was inserted, and the duration of the true astronomical year was compara- f£ tivcly closely approached. Caesar was assisted by the astronomer Sosigenes, and his work was- a monumental one, because ever since, in the countries using that calendar, the month of the year had always been a true index of the season. The Julian calendar, although a great improvement on its forerunners, b: was not perfect because the true year 0) was not quite 3654 days in length. In m 1582 an error of about nine days had m accumulated, and Pope Gregory S£ ordered that they should be omitted from October of that year, and that in afuture leap year should not be ob- m served in any century year, the number of which was not divisible by ri 400. Thus 1900 was not a leap year m but 2000 would be. Under this system A there would be no important error for millenniums to come. The Gregorian *■' calendar was adopted in the year of its E: promulgation or very shortly after- ri wards by countries most closely in touch with the Papal See, but -Pro- li] testant countries were naturally tardy to in taking their cue from it. In Ger- ni many, Holland, and Denmark the inno- CE vation was not generally, adopted until 1700. Britain authorised it in 1752 w Japan in 1873, and China in 1912. Rus- w sia changed over only in 1917, and 1" Greece as late as 1923. F: INEVITABLE CHANGE. B "The present system, although of fo proved value, is not sacrosanct," said fu Mr. Begg in conclusion, "and if re- Pi vision or alteration is demanded by M civil convenience (as it may well be in dc the future) we need have no concern ' as an astronomical society, except to tv conserve consonance with the inexor- w able march of the heavenly bodies, w These furnish us with a frame of refer- te c-nce for measurement and time scale altogether detached from human dc caprice or inconstancy of records. It nc is true that even here secular changes I ca creep in which, although negligible in oc the span of recorded time, will oven- ge tually become manifest. The daily rotation of the earth is gradually be- in coming slower by reason of tidal M action, while the wasting substance lc of the sun, resulting in diminished gravitational pull, is yearly releasing te the earth to a more distant and longer ! \v< orbit. The stars, themselves, which j like the hour-hand of a clock to a! ar casual glance, seem immovable to the 'at ephemeral generations of mankind,! co will in the longer scale melt into new j sti patterns like wisps of smoke. Growing Ita mathematical ingenuity may scrutinise ' these changes to find a stable or cal- co culable order, but it may be questioned ■ th if complete success will ever be! rif attained." ex