Megalithic Studies Mid- Wales. Click for Glossary*Pop-Up glossary and paragraph links. Move mouse over text in this colour and Click.*Click for Glossary *Megalithic Calendar 1 * *CALENDARS. * *2.1.1 * The common theme of calendar making is the desire to organize units of time to satisfy the needs and preoccupations of society. In addition to serving practical purposes, the process of organization provides a sense, however illusory, of understanding and controlling time itself. Thus calendars serve as a link between mankind and the cosmos. It is little wonder that calendars have held a sacred status and have served as a source of social order and cultural identity. From /'The Explanatory Supplement to the Astronomical Almanac'/, P. Kenneth Seidelmann, editor, *2.1.2 *It is not generally appreciated how effective the Christian or Gregorian calendar serves the needs of practical global time keeping today. In order to minimise confusion a good calendar must be mathematically symmetrical and have a simple mnemonic formula for the insertion of intercalary days. In the history of world calendars few methods of dividing the year and systematically updating the calendar have been devised which allow the general populace to keep reliable track of extensive spans of time without regular support from a professional authority. Such authority must be able to provide reliable calculations and relate these to current corrections derived from astronomical observations of the phenomena upon which the calendar is based. ** *2.1.3 * Although some calendars replicate astronomical cycles according to fixed rules, others are based on abstract, perpetually repeating cycles of no astronomical significance. Some calendars are regulated by astronomical observations, some carefully and redundantly enumerate every unit, and some contain ambiguities and discontinuities. Some calendars are codified in written laws; others are transmitted by oral tradition. /'The Explanatory Supplement to the Astronomical Almanac.'/ *Muslim Calendar.* * *2.1.4 *The lunar calendar of most Muslim states has months of 29 and 30 days alternatively. Some Muslims still adhere to the traditional method of identifying the first day of a new month from the evening when the first sliver of the new moon appears in the sky. If cloud obscures the observation then an extra day may be added to the new month if it is a 29er but not if it is a 30er as Muslim law states that no month may be 31 days long. This situation often results in the day of a new moon and dates of religious festivals being in conflict with the published state calendar. *** ***Hindu Calendar.*** *** *****2.1.5 *The Hindu luni-solar calendar has 12 months of 29.5 days each giving a year of 354 days. When this accounting shows a discrepancy from the true solar year of exactly one Hindu month, (29.5 days), an intercalary month is added. As this is only necessary every 32 months the extra month may be added at anytime of year and some years have no additional month. ***** *****Sikh Calendar.***** ***** *****2.1.6 *The lunar calendar of the Sikhs is 365 days long with 12 months varying between 29 and 32 day. ******* *******Jewish Calendar.******* ******* *****2.1.7 *The luni-solar calendar of the Jews is similar to the Muslim accounting having their Regular Common year consist of 12 months of 29 and 30 days alternatively. As this totals only 354 days an extra month must be added in some years. These intercalary years are called Embolistic years or leap years. /All the above calendars have greater or lesser asymmetries making reliable time-keeping, for most people, dependent on authorised, centralised information./ ********* *********The Christian or Gregorian Calendar.********* ********* *****2.1.8 *The luni-solar Roman calendar, before Julius Caesar, had 12 months of 29 and 30 days and required intercalary months of 22 or 23 days every second year. By 46 BC this system had become unmanageable and Julius Caesar enlisted the services of an Egyptian astronomer, Sosigenes, to construct a new calendric system for the use of the Roman Empire. The Julian calendar was inaugurated in 45 BC and required the radical adjustment of having the year prior consist of 445 days. This was known thereafter as the Year of Confusion. The Julian calendar is the basis of the modern Christian calendar with a slight adjustment adopted by Pope Gregory in 1582. With a 12 part calendar having alternate months of 30/31 day lengths, except February, and an intercalary day added in every year divisible by 4 but /_not_/ in any end-of-century year /_not_/ divisible by 400, the Gregorian calendar is the most rational time keeping system in existence and simple enough for most people to keep aligned without specialised knowledge or astronomical skills. Astronomers say that this system will take 10,000 years to move out of phase by 3 days. In times before cheaply distributed information, (the printing press), giving authorised publication of calendric data, the Julian/Gregorian system would have been a great boon to society allowing most people to have a personal grasp of reliable time-keeping for the extent of a human lifetime at least, and the regular 30/31 day alternating months with one anomaly, February, is as mathematically rational as a 12 part division of the true year can be. *********** ***********The British Megalithic Calendar.*********** *********** *****2.1.9 *From a ****large sample of astronomical surveys of megalithic sites, mostly in Scotland and Wales, Alexander Thom has deduced that a solar calendar of 16 parts or 'months' was in use during the period generally termed the Middle Bronze Age, circa 2000 to 1600 BC throughout Britain. This calendar was entirely solar and constructed of 16 epochs or 'months'; 4 of 22 days, 11 of 23 days with one of 24 days. ************* *************Horast1c************* ************* *2.1.10 *With this sky map of ****required declinations in mind the megalithic astronomer could seek for opportunities in the landscape to position a backsight which would align with a horizon feature and a required calendar interval declination in the sky. The 16 part calendar. *************** *2.1.11 * Thom, /Megalithic Sites in Britain/ p108: Let us anticipate and say that in Megalithic remains we do find definite evidence of this kind of division of the year. We saw that when Megalithic man subdivided his units of length he used halves, quarters, and eighths so we need not be surprised to find his year similarly divided. But we also saw that he was capable of measuring long distances counting in tens. He would certainly also count days, otherwise how did he divide the year into two? His obsession with numbers may have led him to produce a calendar which would be numerically correct just as he was led to attempt to produce circles and ellipses which were rational in all their dimensions. *2.1.12 **This method of division achieves even closer symmetry than the 12 month division of the Gregorian calendar. The Gregorian has an average month length of 30.5 days and the anomalistic month, February, with 28 days. This month is 2.5 days short of the average. With the Megalithic calendar the average length of a 'month' is 22.75 days. The anomalistic epoch of 24 days is only 1.25 days greater than the average. *** ****Sky map**** **** *********2.1.13 *This is the celestial template which a megalithic astronomer would carry in mind when judging the astronomical opportunities in a landscape. ****** ************ ****** Each track is the path of the Sun from rise to set at a calendar partition. Finding a position to locate a calendar backsight aligning with a horizon feature and one of the solar calendar tracks is, given room to move, fairly easy. Requiring to find a single position which supports two or more alignments becomes progressively more difficult and backsights supporting several calendar alignments must have taken years of work to establish. Such multi-aligned backsights however may give ****high statistical probability* * against chance for their location. See html page _S1, Llananno._ ****** *2.1.14 * Thom, /Megalithic Sites in Britain/ p108; *The sixteen-month calendar* As the author collected more and more reliable lines from the sites certain groups of declinations began gradually to appear in positions on the histogram which were difficult to explain. These were at or near -22deg, -8deg, +9deg, and +22deg. The group at +9deg might be ascribed to Spica at 1700 B.C., but there were no convenient stars to explain the others. If they are solar then we seek the times of year at which the sun had these declinations. Accepting these dates, we find that with the fully established solstices, equinoxes, May/ Lammas, and Martinmas/Candlemas days the year is divided into sixteen equal parts. The data in the field on which these subdivisions rest is sufficiently convincing and reliable to make it necessary to go into the matter in detail. *2.1.15 **Thom relates how, even with the use of modern mathematical approaches, he could not devise a 16 epoch partitioning of the year which matched the symmetry of the calendar as deduced from his sample of many megalithic astronomical alignments. *** Thom, /Megalithic Sites in Britain/ p110; The criterion of a good solution is that the declinations must pair, that is the day in the autumn should have the same declination as the corresponding day in the spring. The solution obtained by the 22/23-day month did not give very good pairing. Accordingly, it was decided to try to find from the observed declinations what solution Megalithic man had obtained. Weighted means for the six necessary declinations (seven with the equinoctial value) were formed from the observed values ...(gained from high class surveys of over 300 sites). Using these the corresponding dates were read off (two for each mean declination) from a large-scale plot of the theoretical declination curve (Fig. 9.1). Fig.9.1: Fig.9.1 *2.1.16 *It is remarkable that this procedure led to a much better solution than had previously been found. The arrangement of the 'months' is shown in Table 9.1, Thom,/Megalithic Sites in Britain/ p110 Table.9.1; Calendar *Intermediate calendar dates.* *2.1.17 *There is much evidence for the possibility that the calendar was further subdivided. More clumping of data suggested to Thom that four more subdivisions were being indicated in the two calendar epochs on either side of the equinoxes. These would create 8 subdivisions of 11 and 12 day periods in these epochs but little evidence has been found that the other epochs clustered around the solstices had such divisions. ** * * Thom, /Megalithic Sites in Britain/ p116; A possible further subdivision. The improbability that the year was further subdivided into 32 parts of 11 or 12 days is considerably lessened by the accuracy with which certain other- wise unexplained lines support such a subdivision. As some of the lines are Class A it may be desirable to give the evidence and leave it there for future work to decide the matter. As before, guidance in choosing the epochs was obtained partly from the observed declinations and partly from pairing. Ultimately almost complete pairing was obtained with epochs which, it will be seen (Table 9.3, below), retain the eleven- or twelve-day interval, which would thus very likely apply to the whole year although the evidence at present only exists for twenty-four epochs. The calculated declinations for the four necessary extra pairs are given in the table. Thom,/Megalithic Sites in Britain/ p116 Table.9.3; Intermediate It will be seen that the pairing is very good. It is proposed here to call the extra dates suggested above 'intermediate calendar dates'. * * *For recent identification of alignments indicating intermediate Megalithic Calendar dates see html pages; _S1, Llananno/Rhoscrug I_ < rosgrug1.html>, _S2, Llananno/Warren Hill,_ and _Rollright, Oxfordshire._ * **Insertion of an intercalary day, (leap year).** ** ** *2.1.19 **It is not now known when the leap year of the Megalithic Calendar fell nor where the intercalary day was inserted but the need must have been apparent to the megalith builders constrained to slow, trial-and-error methods of constructing their sites. *** * * Thom, /Megalithic Sites in Britain/ p108; From the time of Julius Caesar our calendar has inserted that extra day every fourth year. Was the necessity to introduce a leap year known to Megalithic man? We shall see that it is certain that he used a solar method of keeping a calendar and that it depended on horizon marks subdividing the year. But each mark must have been established by counting days from a zero date in the year, and each mark served to define two different epochs, one in the spring half of the year and one in the autumn half. It not only took years of work to establish these marks but many more years to transport and erect the huge permanent backsights. In the interval the marks would have got so badly out as to be useless if an intercalary day were not inserted. * * *Standardised time-keeping.* * *2.1.20 **That a nationally agreed system of leap year correction was in existence is also indicated by finding that the precise declinations for the 16 calendar intervals are concurrent throughout Britain. **** * * Thom, /Megalithic Sites in Britain/ p108; It is true that these people, having set up the mark, might have stopped keeping a tally of days, simply leaving the marks to give the indications. But the Megalithic culture was widespread and communication essentially slow. To transfer the 'date' from one end of the system to the other meant that the messengers must have counted days as they travelled and having arrived at an isolated community the counting had to go on until a year with suitable weather allowed the marks to be set up. The alternative is to assume that each community began independently the arduous task of establishing its own calendar epochs. This is indeed possible, but when we find indications of the same declinations in Cumberland, Lewis, Wales, and Caithness we must consider the possibility that the calendar dates throughout this wide area were in phase. * * *Indeed if it were not, again, for these rigorous standards of construction maintained throughout Britain we would not be able to positively detect the Megalithic Calendar today amongst spurious data. * **Working constraints of horizon astronomy.** ** ** *2.1.21 *It would be a respectable feat for any society, even with precision optical technology, to achieve such a fine mathematical solution to the partitioning of the year but particularly impressive when we consider that, in the terrain where the high- class work was carried out, the society was principally non-urban pastoralist confined to using very limited observational data only gained at sunrise or sunset. ** **4tonw** ** ** **Four Stones, Walton, Radnorshire, a multi- alignment backsight, north- west quadrant.** ** ** * * Thom, /Megalithic Sites in Britain/ p108; .....since the tropical year (equinox to equinox) consists of 365.25 days, and half a year is 182.625 days. Having set up our mark S and seen the sun rise exactly on it on a day in the spring we may have arranged matters so that the sun rises again on the mark after 182 days or after 183 days but certainly not after 182.625 days. That would be in the afternoon. * * *In effect, for precision transit telescopes, the megalith builders substituted long distance alignments to the horizon emanating from carefully placed back markers and succeeded in identifying one day from another with reliability. This respectable achievement, however, was only the first engineering step upon which was launched a mathematical creation of superb symmetry- a reliable, precise, 16 part partitioning of the year with a further four intermediate divisions. * * * *2.1.22 * **The Megalithic Calendar in Gregorian.** ** ** * * *_Gregorian Calendar Date._ * _*_Megalithic Calendar Interval._ *_ _*_Required declination of the sun._ *_ *21 June. * *CI no 5. Summer solstice. * *+23 deg. 54.3 min. 1800 BC. * *2 June & 12 July. * *CIs 4 & 6. * *+22 deg. 3.6 min. * *7 May.& 6 Aug. * *CIs 3 & 7. Quarter days. * *+16 deg.40.2 min. * *25 April & 18 Aug. * *CIs 2.5 & 7.5. * *+13 deg.13.2 min. * *13 April & 30 Aug. * *CIs 2 & 8. * *+9 deg.9.6 min. * *2 April & 10 Sept. * *CIs 1.5 & 8.5. * *+4 deg. 58.8 min. * *21 March & 21 Sept. * *CIs 1 & 9. Equinoxes. * *+0 deg.26.4 min. 1800 BC. * *11 March & 3 Oct. * *CIs 9.5 & 16.5. * *-3 deg.59.4 min. * *27 Feb.& 15 Oct. * *CIs 10 & 16. * *-8 deg.27.6 min. * *15 Feb.& 27 Oct. * *CIs 10.5 & 15.5 * *-12 deg.39.6 min. * *5th Feb.& 6th.Nov. * *CIs 11 & 15 Quarter days. * *-16 deg.15.6 min. * *11 Jan.& 2 Dec. * *CIs 12 & 14. * *-21 deg.51.6 min. * *21 Dec. * *CI 13 Winter solstice. * *-23 deg.54.3 min. 1800 BC. * * * *All of these Gregorian dates are approximates. The Megalithic Calendar Intervals, (CIs), wander slightly in today's Gregorian calendar due to the differing approaches to maintaining accurate time measurement. These discrapencies may amount to + or - 24 hours around the solstices. Any investigator who wishes to observe or photograph a suspected calendar alignment at or near a Megalithic Calendar Interval should locate, from the current astronomical data tables, the moment in time when the sun reaches the Required Declination for the suspected CI. A CI is a point in time and may not necessarily occur near the sunrise or sunset on the day date given. If, for example, the Required Declination is achieved in the early morning then the nearest sunset will be on the day before and this would be the most accurate set to observe on an alignment which has been engineered to the sunset of this CI. Email here for current updates on the occurrance of megalithic CIs in Gregorian. Reliable sources of astronomical data online can be found in the U.S. Naval Observatory's _data services._ * * * *Information from the Explanatory Supplement to the Astronomical Almanac, P. Kenneth Seidelmann, editor: _*_Calendars and their History by L. E. Doggett._*_ * ** * * Click for Glossary*Pop-Up glossary and paragraph links. Move mouse over text in this colour and Click*Click for Glossary << *The Calendar - **1 */ 2 * */ 3* */ 4* */ 5* * Next>>> Click for Glossary*Interactive Pop Up Glossary. Move mouse over Text and Click*Click for Glossary Email me_with comments or queries- powys@megalithicsites.co.uk_