Our Calendar: Any More Reformers?
V. Vemuri
Why should the New Year's Day fall on 1 January every year? Before we answer this, let us ask, "who determines when a day or a week or a year should start? To most Hindus, for example, the day starts with sun rise. To Westerners, the day starts at midnight. For some, it starts at sun set. See the point?
People in power dominate the way things are done. Until A. D. 800, France celebrated its New Year Day on 1 March. Until A. D. 996, it was 25 March. Then on Easter day until A. D. 1051. Between the 7th century and 1338, the English celebrated their New Year on Christmas day. Starting in 1339, they celebrated two New Year Days: 25 March for civil purposes and Easter for religious purposes. The traditional preference for March is that Spring, which marks the beginning of a new cycle of life, occurs in March in the northern hemisphere where most of the powerful people lived.
So until the middle of the sixteenth century, Europeans celebrated their New Year's Day in late March, as we still do in India. These festivities continued for several days culminating in a celebration on 1 April with an exchange of gifts. Then the king of France authorized a change, and moved the beginning of a new year to 1 January. Many people who either did not get the word or simply refused to change continued to celebrate and exchange gifts on 1 April. Because of this they were called April fools and others mocked them with frivolous gifts and pranks.
Let me get one thing straight. Only in those countries that follow the Gregorian calendar does 1 January count as New Year's Day. In A. D. 1996, according to the Chinese calendar, it is on19 February, the Burmese 15 April, in the Islamic world 19 May, and for the Jews 14 September. In India Ugadi, the Telugu New Year Day, as well as Gudhi Padwa of Maharashtra and Chati Chand of Gujarat fell on March 19.
The complexity of the calendar issue dawned on me after I first noticed that my birthday rarely fell on January 17, the date on which I was born. Not just my birth day. The Telugu New Year's day rarely fell on the same date from year to year. In fact, virtually none of the Hindu festivals fell on the same date, each year. Obviously the Telugu Panchangam we use is not synchronized with our English calendar.
The saga of synchronizing the calendar with the seasons is one of humanity's endearing traits: the inability to get the simplest of the things straight. In spite of repeated reforms, none of the efforts resulted in a perfect calendar. We still have to throw in a fudge factor - a few seconds, perhaps a day or two, or even a month - just to stop days turning into nights or summers into winters. This pathetic situation persists in spite of humanity's valiant efforts. The ultimate blame for this chronic confusion with calendars lies with our Solar System itself; it is not behaving itself.
Our planet rotates on its axis once every 23.9345 hours, or 23 hours 56 minutes and 4 seconds. This time of rotation is relative to the "fixed" stars in the firmament. The "24 hours in a day" is the interval between successive occasions when the Sun is overhead. This slight difference comes because of the following simple fact. While the Earth is rotating, it is also revolving around the Sun, and it takes those extra 3 minutes and 56 seconds for the rotation to catch up with the Sun's apparent slippage with reference to the background stars. Even the 24-hour figure is only an average; the actual length of the day varies because the Earth's orbit is not a perfect circle.
So much for the Sun's behavior. Let us look at the Moon. Relative to the "fixed" stars, the Moon revolves around the Earth once every 27.32166 days. But this is more difficult to observe than the obvious phases of the Moon. These phases, as seen from the Earth, depend upon the relative position of the Sun and Moon. Once again, there is some slippage in Sun's position. So we can only talk in terms of averages. The length of an average "synodic lunar month" is 29.53058 days (synodic in Greek means a religious gathering).
Next, let us look at the year. It is the time it takes for the Earth to travel once around the Sun. This is the "sideral year" of length 365.25636 days. For calendars, the more useful thing is the time between the start of a season in one year to its start the following year. This "tropical year," which is 365.24219 days, is very so much slightly smaller than the sideral year. This comes because of the precession of the equinoxes.
To understand this phenomenon, remember that the Earth's axis is tilted at an angle of 23.5 degrees relative to the ecliptic, the plane of the Earth's orbit. This is responsible for the variations in the day/night division of the 24-hour day. There are two days, each year, when the nights and days are of equal length ("equinoxes" means equal nights). One of these days is the first day of spring and the other the first day of autumn. Incidentally, one of these days would be a good - not perfect - choice for a New Year's Day, a choice based on astronomical rather than emotional factors. Unfortunately, there is a slippage of these equinoxes also. Because of the Earth's bulge at the equator, the Earth wobbles slowly like a spinning top. That is, the axis of Earth's spin precesses, so very slowly, and completes a circular tour every 25, 800 years. Stated differently, instead of pointing at the North Star steadily, the Earth's axis makes a small circle around the North Star. A consequence of this is the equinoxes come a little earlier each year. Modern calendars have yet to deal with this effect.
Indians would be interested to know that because of this movement, the Vedic sky would be significantly different from the contemporary sky. I was told that Varahamihira, who lived long before Newton's theory predicted the precession of the equinoxes, knew about this phenomenon and even offered a correction to this error.
The point to be made is that neither the tropical year nor the lunar month are simple multiples of a day. Indeed, the multiples are irrational numbers, numbers which cannot be represented as fractions. For example, if the tropical year were to be exactly 365.25 days, then 4 years would be exactly 1461 days and all the astronomical events will repeat themselves after every four years. Unfortunately, both the tropical year and lunar month contain an irrational number of days. Also the tropical year contains an irrational number of lunar months. So nothing ever repeats itself exactly; an enticing philosophical thought!
Because of these irregularities, the story of calendars is a history of compromises made in different cultures at different times. Depending on the time and place you choose, there are no less than 26 different New Years.
Calendars fall into two broad categories: solar and lunar. Most lunar calendars include solar related adjustments to keep in tune with the seasons. Our English calendar is solar. In 46 B. C. Julius Caesar reformed the previous Roman lunar calendar. He decreed that the length of a year shall be 365.25 days. He set up a cycle of 1461 days consisting of one leap year of 366 days and three ordinary years of 365 days. He added 96 days to 46 B. C. so spring occurs in traditional mid-March and decreed that the new year start on 1 January. The Roman priests committed an error in inserting the extra day in leap years. So the calendar was reformed again in 10 B. C.
The Julian year exceeds the tropical year by 0.00781 days. So by 1582, the spring equinox slipped back from 21 March to 11 March. To prevent further slippage, Pope Gregory XIII reformed the calendar once more. Leap years thenceforth were omitted in years ending in 00, unless that year happens to be a multiple of 400. To correct the error that had already occurred, ten days of 1582 were removed. This Gregorian calendar is what we all use now.
A good example of lunar calendar is the Muslim calendar. The year consists of 12 lunar months or 354 days, so significant dates and festive days drift relative to the seasons. The months are alternately 30 and 29 days long. The twelfth month, which usually contains 29 days, acquires an extra day in intercalary years 2, 5, 7, 10, 13, 16, 18, 21, 24, 26 and 29 of a repetitive 30-year cycle.
An example of a lunar calendar tuned to accommodate the solar year is the Jewish calendar. This calendar uses a lunar cycle of 19 years with a solar cycle of 28 years. The months have 29 or 30 days. There is also a 30-day intercalary month which occurs only in years 3, 6, 8, 11, 14, 17 and 19 of the lunar cycle.
The future does not look any bright either. All the astronomical cycles are slowly changing their lengths. Because of tidal and gravitational forces, the length of the day, lunar month, and tropical year are increasing. Changes in the tilt of the Earth's axis due to glitches, called Milankovitch shifts, are another factor to reckon with. The final straw on this proverbial camel's back came when it was established in1993 that the motion of objects in the Solar System is chaotic. Due to this, no matter what scheme you use, how carefully you plan and how accurately you calculate, the "butterfly effect" will cause an unpredictable drift away from whatever calendar you calculated in advance. Watch out, astrologers, science says that the future is not predictable!