Everyone knows that the earth spins on its axis, making a complete revolution once a day. That is how we have day and night. Everyone also knows that it takes the earth one year to circle the sun. This creates the seasons because the earth is tilted at an angle of 23.5 degrees relative to the sun. Thus New Yorkers, for example, spend winter tilted away from the sun and summer tilted towards it.
Less people know that the world also wobbles. Just as a Chanukah dreidel makes a circular wobble when it starts to slow down, the world also has a wobble – a very slow wobble. In about 3631/130 BCE, the Greek astronomer Hipparchus calculated that it takes about 26,000 years for this wobble to complete one circuit. Three hundred years ago, Sir Isaac Newton figured out that the cause of this wobble is that the earth bulges at the equator. The sun, moon and planets tug at the bulge, trying to make the tilted world stand “upright,” and this makes the world wobble.
This wobble created a calendar anomaly which gentile savants have wrestled with for centuries. Hillel II, however, anticipated the problem when he established the Jewish calendar, in about 3980/330, and our Yomim Tovim are still in sync. As the Chazon Ish (Orach Chaim 138:4) writes, certain aspects of the Jewish calendar are based on Sinaitic tradition.
THE JULIAN CALENDAR
The saga began in Julius Caesar’s time when it was decided, after centuries of celestial observations that the solar year is about 365¼ days long.
At first, ancient Egyptians calculated the year’s length with a Nilometer. Every year, melting snow in Ethiopia and Uganda causes a huge mass of water to surge down the Nile river, reaching a high water mark on almost the same exact day each year. To know when a year had passed, all one had to do was embed a tall reed along the riverbank and cut a notch to measure the high water mark. The water hit the notch again about a year later.
Then the Egyptians noticed another phenomenon. As the Gemara tells us, there are different constellations in the sky every month. This is because the world orbits around the sun and faces a different sector of space every night, and it takes a year for the earth to get back to the same place. Noting the exact time Sirius (the Dog Star) rose in a direct line with the sun each year, the Egyptians fine-tuned their observations and calculated that the year is a quarter of a day longer than 365 days.
In 3645/46 BCE, Julius Caesar declared that this was the official length of the Roman Empire’s years. Before that, the Roman year had been 355 days long. To bring his new calendar in line with the first day of Spring which was traditionally on March 25, that year was stretched out an incredible 445 days. Caesar triumphantly named this year the “ultimus annus confusionis,” “the last year of confusion,” while disgruntled Romans called it “the Year of Confusion.” At the same time, Caesar established that secular months would be 30 or 31 days long, except for February that is usually 28 days long, but 29 days long every four years, to account for the four quarter- days of the past four years.
TWO KINDS OF YEARS
Two halachos are based on the length of the solar year: Birkas HaChamah and the date we begin saying “V’sein tal u’matar livracha” in the Diaspora. Birkas HaChamah is said on the 4th of Nisan every 28 years and commemorates the sun returning to the same position it was in at the time of the Creation. Why does this occur every 28 years? Because of the extra six hours at the end of each year, it works out that the sun is only at the exact same place in the sky as at the time of its creation, at the same hour and on the same day of the week, once every 28 years. Secondly, the Gemara (Taanis 10a) instructs Jews outside Eretz Yisroel to begin saying “V’sein tal u’matar” sixty days after the beginning of Fall. We start saying it on December 4, which is correct according to Caesar’s calendar. According to the modern calendar, we would start this about twelve days sooner.
However, Caesar’s 365 ¼ year is based on the stars and not on the seasons. Astronomers calculating the time between one equinox (the beginning of spring and fall when day and night are equal) and another, discovered that the resultant year is about eleven minutes shorter than the Julian calendar’s star-based year. This difference is crucial because it adds up to about one day’s difference every 128 years.
In other words, astronomers realized that there are two kinds of solar years, the sidereal year of 365¼ days, which is measured by observing the stars, and the tropical year (eleven minutes shorter than the sidereal year), which is calculated by measuring between the equinoxes.
But how is this possible? Aren’t the seasons dependent on the earth’s annual journey around the sun, and isn’t this annual journey measured by observing the stars? The discrepancy is caused by the earth’s wobble that we discussed at the beginning of this article.
Imagine that you are traveling on a train that is so long that it takes eleven minutes to pass any given point. Let’s say the train takes one day to travel a round-trip journey from New York to Los Angeles. If someone at the back of the train walks to the front coach during the journey, he will arrive in New York eleven minutes earlier than if he had stayed in the last coach. Similarly, the world seems to take 365¼ days to get back under the same star because it wobbled westwards. In actuality, it takes the world eleven minutes longer than that to reach the same place where it was a year before.
The seasons are governed by this shorter, tropical year. Actually, Ptolemy and other Alexandrian scientists already knew about this discrepancy in Caesar’s time, but he ignored their opinion.
THE POPE’S SOLUTION
In about 4927/1267, the scientifically minded English friar, Francis Bacon, shot off an urgent letter to Pope Clement IV, warning him that the extra minutes at the end of each year had already accumulated to nine extra days. If this went on, he warned, March would drift back into midwinter.
Bacon advised nothing less than chopping nine days off the calendar to fix it, and dropping a day off the calendar every 125 years after that. Bacon risked being branded as a heretic by indicating that the gentile holy days were being celebrated on the wrong day.
It took the church three centuries to react. On 24 January, 5342/1582, Pope Gregory XIII signed a bull that officially abolished Julius Caesar’s calendar and ushered in the new Gregorian calendar used worldwide nowadays. To compensate for the extra eleven minutes a year, a new rule was publicized. Until then, every year divisible by four was a leap year. From then on, centurial years that were not evenly divisible by 400 would not be leap years even if they were divisible by four. Therefore 1700, 1800, 1900 and 2100 are not leap years, while 1600, 2000, and 2400 are leap years. On March 1 that year, notices were posted throughout Rome declaring that henceforth the world would be run by the new calendar. What about the ten extra days gained since Julius Caesar’s time? The Pope wrote them off like a bad debt. Anyone waking up in the Pope’s domain on October 5 that year instantly “lost” ten days of his life. The calendar had jumped to October 15.
This took some getting used to. “I grit my teeth but my mind is always ten days ahead or ten days behind,” an Italian wrote six years later. “It keeps muttering in my ears: ‘That adjustment concerns people not yet born.’”
Sailors, shopkeepers and kings worried about lost work days, uncollected taxes and deadlines arriving ten days early. In Frankfurt, there was a riot against the Pope and his mathematicians, whom the people were convinced had conspired to steal a chunk of their lives.
Protestants were convinced that the Pope’s amendment was a Trojan horse designed to trick good gentiles into observing the incorrect holy days. They suspected that it was a strategy to extend the Pope’s authority worldwide.
“We do not recognize this Lycurgus (a Greek who reformed Spartan law), this calendar maker…,” wrote John Heerbrand in Germany. “All his loathsome and abominable errors, his sacrilegious and idol-worshipping practices, his vicious, perverse and impious dogmas… these, little by little, he will once more insert into our churches.”
But the world could not ignore the facts for ever, and gradually adopted the new calendar. When England changed over in 5512/1752, a bemused correspondent expressed his confusion in the popular Gentleman’s Magazine:
“I write to you in the greatest perplexity. I desire you’ll find some way of setting my affair to rights or I believe I shall run mad and break my heart into the bargain. How is all this? I desire to know plainly and truly! I went to bed last night, it was Wednesday, Sept. 2, and the first I cast my eye upon this morning at the top of your paper was Thursday, Sept. 14. I did not go to bed at all between one and two. Have I slept away eleven days in seven hours, or how is it? For my part, I don’t find I’m any more refresh’d than after a common night’s sleep.
“They tell me there’s an Act of Parliament for this. With due reverence be it spoken, I have always thought there were very few things a British Parliament could not do, but if I had been ask’d, I should have guess’d that the annihilation of time was one of them!”
China accepted the Gregorian calendar in 5719/1949, and among the remaining few who still observe the old calendar are Jews in their observance of “Birkas HaChamah” and “Birkas Geshamim” as we mentioned earlier. A subsequent article, IY”H, will discuss the Gedolim’s view on this subject, and how Hillel II avoided the eleven-minute problem in the calendar he established almost 2,000 years ago.