Astral themes

The sky is the most mysterious part of our everyday experience. Familiarity may make the amazing events going on at ground level seem almost ordinary. Plants and animals grow and die, rain falls, rivers flow. We feel we understand that.

But the sky is beyond comprehension. Two great objects travel through it, one hot and constant, the other cold and changeable. In the daytime it is moody; there may be blazing sun, or racing clouds, or darkness followed by thunder and lightning. And yet on a clear night the sky is the very opposite - predictable, if you look hard enough, with recognizable groups of stars moving in a slow but reliable manner.

Man's interest in the sky is at the heart of three separate stories - astronomy, astrology and the calendar.

Astronomy is the scientific study of sun, moon and stars. Astrology is a pseudo-science interpreting the supposed effect of the heavenly bodies on human existence. In early history the two are closely linked. The sky is the home of many of the gods, who influence life on earth. And the patterns in the sky must surely reflect that influence.

Days months and years

Compilers of a calendar, attempting to record and to predict the passage of time, are offered an easy first step in the cycle of the moon.

The only two measures of time available to primitive people are the day (the space between two nights) and the month (the space between new moons). The month is a well adjusted length of time for recalling fairly recent events, and it has a magic significance through its loose link with the female menstrual period. A far more important slice of time is the year, a full circuit of the earth round the sun - crucial in human activities because of its influence on seasons and crops. But the length of a year is exceptionally hard to measure.

Primitive societies make do with a broad concept, counting the year as starting when leaves sprout on a particular tree or describing someone as having lived through a certain number of harvests.

The only simple yet accurate way of measuring a year is in relation to the stars (though structures such as the passage grave at Newgrange can record an annual position of the sun, at a considerable cost in effort). The stars appear in the night sky at different times and places depending on where the earth is in its orbit round the sun. A star observed in a given place - on the horizon at dawn, for example - will be there again exactly a year later.

In Egypt the temple priests derive much of their prestige from close attention to the stars, enabling them to give the impression of predicting natural events. The best example is their use of Sirius, the Dog Star. It rises above the horizon just before dawn at the time of year when the all-important flooding of the Nile is about to occur. Priests who can foretell this great event are powerful soothsayers.

This observation of Sirius also enables the Egyptians to become the first people to move from a lunar to a solar calendar.

Lunar and solar years

In Mesopotamia, where the Babylonians are the leading astronomers, the calendar is a simple lunar one. So probably is the first Egyptian calendar. And a lunar calendar is still in use today in Islam. But such a calendar has one major disadvantage.

The length of a lunar month, from one new moon to the next, is 29.5 days. So twelve lunar months are 354 days, approximately 11 days short of a solar year. In a lunar year each of the twelve months slips steadily back through the seasons (as happens now with the Muslim calendar), returning to its original position only after 32 years.

In some lunar calendars an extra month is inserted from time to time to keep in step with the solar year. This happens in Mesopotamia and in republican Rome, and it remains the case today in the Jewish calendar.

But the Egyptian priests' observation of Sirius enables them to count the number of days in a solar year. They make it 365. They then very logically adjust the twelve months of the lunar year, making each of them 30 days long and adding 5 extra days at the end of the year. Compared to anybody else's calendar at the time this is very satisfactory. But there is a snag.

The priests cannot have failed to notice that every four years Sirius appears one day later. The reason is that the solar year is more exactly 365 days and 6 hours. The Egyptians make no adjustment for this, with the result that their calendar slides backwards through the seasons just like a lunar one but much more slowly. Instead of 32 years with the moon, it is 1460 years before Sirius rises again on the first day of the first month.

It is known from the records that in AD 139 Sirius rises on the first day of the first Egyptian month. This makes it certain that the Egyptian calendar is introduced one or two full cycles (1460 or 2920 years) earlier, either in 1321 or 2781 BC - with the earlier date considered more probable.

Julian and Mayan calendars: 1st century BC

The Roman calendar introduced by Julius caesar, and subsequently known as the Julian calendar, gets far closer to the solar year than any predecessor. By the 1st century BC reform in Rome has become an evident necessity. The existing calendar is a lunar one with extra months slipped in from to time in an attempt to adjust it. In Caesar's time this calendar is three months out in relation to the seasons.

On the advice of Sosigenes, a learned astronomer from Alexandria, Caesar adds ninety days to the year 46 BC and starts a new calendar on 1 January 45.

Sosigenes advises Caesar that the length of the solar year is 365 days and six hours. The natural solution is to add a day every fourth year - introducing the concept of the leap year. The extra day is added to February, the shortest of the Roman months.

Spread through the Roman empire, and later throughout Christendom, this calendar proves very effective for many centuries. Only much later does a flaw yet again appear. The reason is that the solar year is not 365 days and 6 hours but 365 days, 5 hours, 48 minutes and 46 seconds. The difference amounts to only one day in 130 years. But over the span of history even that begins to show. Another adjustment will eventually be necessary.

While Julius caesar is improving on the solar calendar of 365 days, a similar calendar has been independently arrived at on the other side of the Atlantic. Devised originally by the Olmecs of central America, it is perfected in about the 1st century AD by the Maya.

The Maya, establishing that there are 365 days in the year, divide them into 18 months of 20 days. Like the Egyptians (who have 12 months of 30 days), they complete the year by adding 5 extra days at the end - days which are considered to be extremely unlucky for any undertaking. An unusual aspect of the Mayan system is the Calendar round, a 52-year cycle in which no two days have the same name.

The working week

Unlike the day, the month or the year, the week is an entirely artificial period of time. It is probably first made necessary by the demands of trade. Hunter-gatherers and primitive farmers have no need of such a concept, but commerce benefits from regularity. The original weeks are almost certainly the gaps between market days.

Weeks of this kind vary from four days among some African tribes to ten days in the Inca civilization and in China. In ancient China a five-day week sets the working pattern for the Confucian civil service, every fifth day being a 'bath and hair-washing day'. Later this is extended to a ten-day week, with the three periods of each month known as the first, middle and last bath.

There are two possible sources for the seven-day week. One is the Biblical creation story. From those times the Israelites have a week of this length, with the seventh day reserved for rest and worship (a pattern reflected in the Bible's account of creation).

The other and more likely source is Rome, where the equivalent of the modern week is adopted in about the 1st century AD - a time and a place where the Jewish tradition would have little influence. The number of days in the week derives probably, through astrology, from the seven known planets - which also provide the names of the days (see Days of the week).

Jewish and Muslim calendars

The Jewish calendar combines lunar and solar cycles. It is given its present form in921 after a great debate between supporters of two slightly different systems.

In origin the calendar goes back to the captivity in Babylon, when the Jews adopt the Babylonians' calendar and their names for the months. They are lunar months of 30 or 29 days. In every second or third year an extra month of 30 days is added to keep the calendar in approximate step with the solar year. This constitutes a crucial difference between the Jewish and Muslim systems.

The Muslim calendar is the only one in widespread use to be based uncompromisingly on lunar months, with no adjustments to bring the years into balance with the solar cycle.

The twelve months are alternately 29 and 30 days long (the lunar cycle is approximately 29.5 days), giving a year of 354 days. There are two significant results. Muslim months bear no relation to the seasons, and Muslim years do not coincide with those of other chronologies. There are about 103 lunar years in a solar century. By the millennium there will have been 1421 lunar years but only 1378 solar years from the start of Muslim chronology in Ah 1 or622. The year Ah 1421 will be2000.

Gregorian calendar: AD 1582-1917

By the 16th century the seemingly minor error in the Julian calendar (estimating the solar year to be 11 minutes and 14 seconds shorter than it actually is) has accumulated to a ten-day discrepancy between the calendar and reality. It is most noticeable on occasions such as the equinox, now occuring ten days earlier than the correct calendar dates of March 21 and September 23.

Pope Gregory XIII employs a German Jesuit and astronomer, Christopher Clavius, to find a solution. Calculating that the error amounts to three days in 400 years, Clavius suggests an ingenious adjustment.

His proposal, which becomes the basis of the calendar known after the commissioning pope as Gregorian, is that century years (or those ending in '00') should only be leap years if divisible by 400. This eliminates three leap years in every four centuries and neatly solves the problem. The result, in the centuries since the reform, is that 1600 and 2000 are normal leap years, but the intervening 1700, 1800 and 1900 do not include February 29.

Gregory puts the proposal into immediate effect in the papal states, announcing that the day after October 4 in 1582 will be October 15 - thus saving the lost ten days.

The pope's lead is followed in the same year by Spain, Portugal, France and most Italian states. The German-speaking Roman Catholic states comply in 1583.

Other Christian realms drag their feet on the issue, reluctant to admit that the pope in Rome has a point. The Lutheran states of Germany change in 1700. Great Britain delays until 1752, by which time the gap is eleven days. Some of the British prove exceptionally dim over the issue, fearing that their lives are being shortened and in places even rioting for the return of the missing days. Imperial Russia never makes the change; it is introduced after the revolution, in 1918. (Potentially confusing dates, near the change-over years, are identified by historians with the codes OS or Old Style for the Julian version and NS or New Style for the Gregorian equivalent.)

More precise measurements in the 20th century have introduced a further refinement of the Gregorian calendar, though not one of immediate significance. As adjusted for pope Gregory, the present system adds one day in every 3,323 years. The accepted solution is that years divisible by 4000 will not be leap years.

February 29 will therefore be dropped unexpectedly in 2000 years' time. In4000, even though the year is divisible by 400, March 1 will follow February 28 in the normal way. Julius caesar and Sosigenes would no doubt be impressed by this ultimate refinement of their system, making it accurate to within one day in 20,000 years.

French republican calendar: AD 1793

The calendar devised during 1793 by a committee of the Republican convention in Paris combines the rational and the impractical in a way characteristic of much French revolutionary activity. It is entirely logical and slightly ridiculous.

The intention is to celebrate the French introduction of a new world era and to sweep away the religious superstitions of the past. By a happy coincidence the first day after the abolition of the monarchy in 1792 is the autumn equinox (September 22), suggesting that even the planetary system recognizes a new beginning. This date now becomes the first day of Year I in the republican calendar.

The Gregorian reform of the calendar has established the necessary system of leap years, which the committee can only follow. However they are free to divide the 365 days of the normal year on a more rational basis than the traditional Months and weekdays. They go for twelve Months of 30 days, subdivided into three Weeks of 10 days (with a day of rest on every tenth day rather than every seventh, implying a revolutionary increase in productivity).

The five extra days are grouped as holidays at the end of the year and are called sansculottides. (A sans-culotte, meaning 'without knee-breeches', is the contemporary phrase for a revolutionary - describing someone radical enough to wear the more informal trousers).

The ten weekdays are named unimaginatively by their numbers, but a great deal of effort is put into finding vivid names for the Months. These are devised by the poet Fabre d'Églantine, a close friend of Danton's (they die together on the scaffold six Months after the calendar is adopted).

Fabre d'Églantine's names reflect the changing weather and crops of the year, with considerable effort being made to find verbal rhythms to suit the moods of the seasons. His Months are Vendémiaire, Brumaire, Frimaire (the autumn), Nivôse, Pluviôse, Ventôse (winter), Germinal, Floréal, Prairial (spring), Messidor, Thermidor, Fructidor (summer).

A satirical version is immediately provided by George Ellis, an English poet deeply hostile to French revolutionary pretensions. He translates d'Églantine's efforts (beginning in January 1 with Nivôse) as: 'Snowy, Flowy, Blowy, Showery, Flowery, Bowery, Hoppy, Croppy, Droppy, Breezy, Sneezy, Freezy'.

The system is imposed by the French on all the sister republics set up in Europe from 1795 (though as a calendar for a new world era it is unfortunate that the names of the Months only match the seasons in the northern hemisphere). However it is abruptly dropped by Napoleon in 1805, when he wants to improve relationships with the pope. France reverts to the Gregorian calendar on 1 January 1806.