The Great Year (ὁ μέγας ἐνιαυτός) is the name given at Delphi for the year at the end of the 8 year cycle (often referred to as “the 9th year”). It is also used to refer to other cycles of time in the anicent Greek world, but the Delphic usage is the primary context used on this site.
The Four Year Cycle, with great years marked
| Nth Hemisphere (~July) | Sth Hemisphere (~January) | Great Year? |
|---|---|---|
| 2023 | 2024 | ✔︎ |
| 2027 | 2028 | |
| 2031 | 2032 | ✔︎ |
| 2035 | 2036 | |
| 2039 | 2040 | ✔︎ |
| 2043 | 2044 | |
| 2047 | 2048 | ✔︎ |
| 2051 | 2052 | |
| 2055 | 2056 | ✔︎ |
| 2059 | 2060 |
See also Enneateric & Pentaeteric Festivals
i.e: 50 months is greater than 49 months; the great year happens at the end of the four year block of 50 months. Or the 4 year group “composed of years without any fraction, as all Great Years should be” as Censorinus has it.
The 8 year cycle contains 3 intercalculatory months. Robert Hannah splits this up as 1 in the first half, and 2 in the second. This matches up with 2023-2024 being a great year/9th year. The next 4 years produce 1 inter calculatory month, and the following 4 after that produce 2.
If this was so, then the Games would have been celebrated at unequal intervals alternately of 49 and 50 months. The reason for this is that in order to keep the festival in the same lunar month for every celebration, while still keeping the lunar calendar as a whole closely tied to the sun, it would be necessary to intercalate one month in the first four years, and two months in the second four-year period. Therefore, in the first four-year period (a quadriennium), instead of having an interval between festivals of just 48 lunar months (4 x 12), the octaeteris would require the inter calation of one month, bringing the interval to 49. In the second quadrien nium, the octaeteris requires the intercalation of two further months, to be added to the intervening 48. If we check Table 1, the Games would be held first in month ii of year 1 of the cycle. Maintaining attachment to month ii, the next celebration would be in year 5, by which time an intercalary month has been added (in year 3). Then the next Games would occur in year 9, by which time two further intercalary months have been added (to years 5 and 8).
– Robert Hannah,
Greek and Roman Calendars: Constructions of Time in the Classical World
§ 18.1 THE GREAT YEAR
Having said enough in regard to the centennial interval I shall now speak of the Great Year, of which the length is greatly varied, whether in the usages of the people or in the traditions of authors; some making it consist in the revolution of two ordinary years, others in the union of many thousands. I will try to explain these differences. The ancient people of Greece having remarked that during the time of the annual revolution of the sun, there are about thirteen risings of the moon, and as these occur with more exactness when two years are taken together, thought that the natural year corresponded to twelve and a half lunar months.
They thus established their civil years in such a manner that with the aid of an intercalation, some are composed of twelve months and others of thirteen, called each isolated year a solar year, and the union of the two, a Great Year. They called this space of time trieteries (a cycle of three years) because the intercalation took place every third year; although the revolution was accomplished in two years and was in reality but a dieteries (a cycle of two years). This is why the mysteries celebrated in honour of Liber Pater are named trieteries by the poets.
This error was subsequently acknowledged; they doubled the space 21 of time and established tetraeteries (a cycle of four years) which returning every fifth year was called pentaeteries. The great year, thus formed of four years, was more convenient, in that the solar year was composed of about 365 1/4 days and this fraction enabled a full day to be added every fourth year. This is why that on the return of every fifth year the games were celebrated in Elis in honour of Jupiter Olympius and at Rome in honour of Jupiter Capitolinus.
§ 18.9 But this space of time, which only coincides with the course of the sun and not with that of the moon, was again doubled; and it was called octaeteries (a cycle of eight years) then called euneaeteries (a cycle of nine years) because this new year returned on the ninth year. This period of time was considered throughout nearly all of Greece, as the real Great Year, because it is composed of years without any fraction, as all Great Years should be. In effect, this was composed of eight full years and 99 full days. The institution of this octaeteries is generally attributed to Eudoxus of Cnidus, but it is said that Cleostrates of Tenedos was the first to invent it, and after him came others who, with the aid of different intercalations of months, have each composed an octaeteries. Thus Harpalus Nauteles, Mnesistratus and others calculated such periods; amongst them Dositheus, whose work is called the Octaeteries of Eudoxus. It is from this cycle that in Greece many religious festivals were celebrated with great ceremony. At Delphi, the games called Pythian were anciently celebrated every eight years.
The games are said to have started on an eight year cycle, in a time before we have records, and then moved to once every 4 years (Note: whether it ever was on an eight year cycle or not is contested, but the ancients believed it was). They were held in the 3rd year of the Olympiad. This corrosponds with 2023, 2027, ...
The earliest attested Python games may have been on the great year, and the following one on the 4 year cycle. There are 2 seperate ancient attempts to date this (4 years apart). That in itself could have been an attempt to fit it back into the 8 year cycle. The commonly accepted date of the formation of the games - the later one - is following a conflict, so it seems reasonable to think of that advent as the exceptional one / the one not conforming to the 8 year cycle.