"Professor," said May, turning on the sofa where she was lying, "Jack has brought me a calendar that runs for ever so many years. You know the doctor says I'll not be well for two whole years, or perhaps three. I have been wondering what month among them all I shall be able to run about in; and then I began to think who could have made the first calendar, and what led him to do it."

"That's very simple, May. Old Father Time just measured the days off with his hour-glass in the first place, and marked them down with the point of his scythe. The world has known all about it ever since."

"Please don't, Jack. Let the Professor tell."

"It would be hard, May, to tell who made the first calendar," answered the Professor. "All nations seem to have had their methods of counting the years and months long before they began writing histories, so that there is no record of the origin of the custom. The Book of Genesis mentions the lights in the heavens as being 'for signs and for seasons, and for days and years.' And Moses uses the word year so often that we see that it must have been common to count the years among those who lived before him."

"The number 1880 means that it is so many years since the birth of Christ, does it not?" asked Joe.

"Yes," said the Professor, "it has been the custom among Christian nations to reckon the years from that great event. They began to do this about the year of our Lord 532."

"Why did they wait so long?" asked Joe.

"You know," he said, "that at first the Christians were very few and weak; during the first three hundred years they had all they could do to escape with their lives from their enemies. But after that they became very numerous and powerful, and were able to establish their own customs. So in 532 a monk named Dionysius Exiguus proposed that they should abandon the old way of counting the years, and adopt the time of the birth of Christ as a starting-point. He thought this would be a very proper way of honoring the Saviour of the world. So he took great pains to find out the exact time when Christ was born, and satisfied himself that it was on the 25th day of December, in the 753d year from the foundation of the city of Rome. The Roman Empire at one time included most of the known world; and the Roman people, proud of their splendid city, counted the years from the supposed time of its being founded. At first the Christians did the same; but they were naturally pleased with the idea of Dionysius."

"Was he the first man who tried to find out what day Christmas came on?" asked Joe. "I should think everybody would have been anxious to know all about it."

"Doubtless there was much interest on the subject. But you know the early Christians had no newspapers, and very few books. Scarcely any of them could even read. Besides, it was very difficult in those times to travel or gain information; and it was dangerous to ask questions of the heathen, or for a man to let them suspect that he was a Christian. And then when we consider that the calendar was in confusion, because even the wisest men did not know the exact length of the year, and there were various ways of counting time, we need not be surprised that the Christians disagreed and made mistakes as to the time when the Saviour was born. In the fourth century, however, St. Cyril urged Pope Julius I. to give orders for an investigation. The result was that the theologians of the East and West agreed upon the 25th of December, though some of them were not convinced. The chief grounds of the decision were the tables in the public records of Rome.

"But let us return to Dionysius. His idea of making the year begin on the 25th of December was thought to be rather too inconvenient, and so the old commencement on the first day of January was retained, as the Romans had arranged it. But the plan of Dionysius was carried out with regard to the numbers by which the years were to be named and called. Thus the year which had been known as 754 became, under the new system, the year 1. And the succession of years from that year 1 is called the Christian era. To get the numbers of its years you have only to subtract 753 from the years in the Roman numbering."

"If we add 753," said Joe, "to 1880, will we get the number of years since old Rome was founded by Romulus and Remus?"

"Yes," said the Professor; "the rule works both ways. There is, however, some uncertainty as to whether the Romans themselves were correct in regard to the age of their city. Very early dates are hard to settle."

"Where did the months get their names?" asked May, "and how did months come to be thought of at all?"

"The months were suggested by the moon. In most languages the word month is very nearly like moon, as you see it is in ours. From new moon around to new moon again is about twenty-nine days, which is nearly the length of a month. The exact time between two new moons is a very puzzling problem. It always involves a troublesome fraction of a day, and is, in fact, never twice alike. So it was found convenient to divide the year into twelve parts, nearly equal, and to call each one a month."

"Why didn't they make them just equal?" asked Gus.

"To do so would have made it necessary to split up some of the days, which would have been awkward. If you divide the 365 days of the year by twelve, there will be five remaining."

"How was it found out that the year had 365 days in it?" asked Joe.

"It took the astronomers to do that," said the Professor; "and until nations became civilized enough to study astronomy accurately, they did not know the number of days in the year. This, however, did not prevent them from being able to count the years, because they could know that every time summer or winter came, a year had passed since the last summer or winter. But now the length of the year—that is, the time occupied by the earth in going completely round the sun—is known within a fraction of a second."

"Was it worth while to go into it so precisely?" asked May. "Would it not have been enough to know the number of the days?"

"By no means," said the Professor. "For then the calendar could not have been regulated so that the months and festivals would keep pace with the seasons. If 365 days had been constantly taken for a year, Christmas, instead of staying in the winter, would long since have moved back through autumn into summer, and so on. In about 1400 years it would travel through the entire circle of the seasons, as it would come some six hours earlier every year than it did the last. In like manner the Fourth of July would gradually fall back into spring, then into winter; and the fire-works would have to be set off in the midst of a snow-storm. The old Romans saw the difficulty; and, to prevent it, Julius CÆsar added an extra day to every fourth year, which you see is the same thing as adding one-fourth of a day to each year, only it is much more convenient. This was done because the earth requires nearly 365¼ days to move round the sun. The year that receives the extra day is called, as you know, leap-year. But even this did not keep the calendar exactly right. In the course of time other changes had to be made, the greatest of which was in 1582, when Pope Gregory XIII. decreed that ten entire days should be dropped out of the month of October. This was called the change from Old to New Style."

"It was rather stupid," said Gus, "to shorten the pleasantest month in the whole year. I would have clipped December or March."

"Please don't forget to tell us," said May, "how the months got their names."

"The first six of them were called after the heathen deities, Janus, Februus, Mars, Aphrodite, Maia, and Juno; July was named after Julius CÆsar, the inventor of leap-year; August after Augustus the Emperor. The names of the last four months simply mean seventh, eighth, ninth, and tenth."

"But," said Joe, "December is not the tenth month, nor is September the seventh."

"That is true," said the Professor; "but those names are supposed to have been given by Romulus, who arranged a year of only ten months, and made it begin with March. His year only had 304 days in it, and was soon found to be much too short. So the months of January and February were added, and instead of being placed at the end, they came in some way to stand at the beginning."

"Now please tell us about the names of the days of the week, and we will not ask any more questions."

"They were called after the sun, moon, and five planets known to the ancients, Mars, Mercury, Jupiter, Venus, and Saturn. You easily recognize sun, moon, and Saturn, Tuesday, Thursday, and Friday are from names given by some of the Northern tribes of Europe to Mars, Jupiter, and Venus. Mercury's day seems scarcely at all connected with his name, but comes from Wodin, who was imagined to be chief among the gods of those barbarous tribes."