Akan calendar

The Akan people (a Kwa group of West Africa) appear to have used a traditional system of timekeeping based on a six-day week (known as "nnanson" "seven-days" via inclusive counting). The Gregorian seven-day week is known as 
"nnawɔtwe" (eight-days). The combination of these two system resulted in periods of 42 days, known as "adaduanan" (meaning "forty days").
Nnanson.
The composition or construction of the Adaduanan cycle appears to be based on an older six-day week.
The six-day week is referred to as "Nnanson" (literally seven-days) and reflects the lack of zero in the numbering systems; the last day and the first day are both included when counting the days of a week.
Nnawɔtwe.
The seven-day week is referred to as "Nnawɔtwe" (literally eight days). Like "Nnanson" the last day and the first day are both included when counting the days of a week.
Adaduanan.
When the six-day week is counted side-by-side with the seven-day week it takes a total of 42 days to reach all combinations. The result of these combinations is shown below; the four "dabɔne" are in italics:
The 42-day cycle shown here, as recorded in Kwahu, is the same recorded for the Brong (i.e., Bono Techiman) a state northwest of the Asante.
Dabɔne.
Within the Adaduanan cycle are found four special days collectively called "dabɔne" ("bɔne", evil); "Fɔdwo", "Awukudae", "Fofi" and "Akwasidae".
The 42-day cycle may be thought to begin on "Fɔdwo" and the other three "dabɔne" follow in nine-day intervals; "Awukudae" on the tenth day, "Fofi" on the nineteenth day, and "Akwasidae" on the twenty-eighth day. It takes a further 14 days to complete the Adaduanan.
When "Kurow" (from "kurow", town) of the six-day week coincides with a Wednesday of the seven-day week (on "Kurow-Wukuo"), or with a Sunday of the seven-day week (on "Kurow-Kwasi"), the two "dabɔne" most closely related to stool rites, "Awukudae" and "Akwasidae" ("Wuko-Adae" and "Kwasi-Adae") are celebrated.
These two 'bad' days, related to death, are called "adae" (perhaps deriving from "da", sleep, "dae", slept or died or dream and "eye", well [sic], implying that the ancestors should lie comfortably in their death), and are closely associated with politico-ritual symbols of gerontocracy sanctified or sanctioned by ancestor veneration.
No funerals may be held and no news of death may reach the ears of a chief (the living shrine of his ancestors) while libations of alcohol and offerings of food are made to the blackened stools (the permanent physical shrines of those ancestors) on an "adae".
When "Fo" of the six-day week coincides with a Monday or Friday, the two "dabɔne" most closely related to tutelary spirits, "Fɔdwo" and "Fofi", are celebrated. They are closely associated with medico-religious symbols or purification and the intervention of anthropomorphic spirits inhabiting natural objects such as rivers and caves.
The Asante sent messengers to Brong (i.e., Techiman) when in doubt about when to hold any festival, for the Brong were 'keepers of the King's calendar.'
These four 'holidays' are not complete vacations from all labour. No farming may be carried out on any "dabɔne" but work per se is not banned. Hunting and gathering are usually permitted and the people may go to their farms to carry home firewood or food reaped the previous day, so long as no weeding of farms is done. Often communal labour is performed on those "dabɔne" which are not filled with ritual and ceremonial activities.
God Days.
Apart from the four standard "dabɔne", some gods may celebrate other days of the cycle, for example, the god Burukung, who was the senior god of the Guan on the Kwawu Afram Plains, and now the chief of the Kwawu abosom (tutelary spirits), since the sixteenth century Akan take-over of Kwawu (the principle shrine being a large, striking inselberg on the northern slopes of the Kwawu escarpment), celebrates the principal rites on "Kwadwo" (the Monday following "Akwasidae").
The cult of Akonnedi, god of Late (Larteh) in Akwapim, which has branches in Kwawu, observes its most frequent public rites on "Nkyi-Mene" or "Memenada Adapa" (the day prior to "Akwasidae").
Various other gods in Kwawu are honoured on various other days in the 42-day cycle.
Solar Year.
The Adaduanan (This means 40 days, and 40 x 9 = 360, and the 9th Akwasidae is celebrated as Odwira, being the end of the past year and the beginning of the new year. Because Akwasidae must be on Sunday the 365 days occurs after the Odwira) do not precisely comprise the annual calendar, because nine cycles total 378 days instead of 365. Eight cycles yield only 336 days. Annually celebrated rites of the different Akan groups, such as the first yam eating festival, "Odwira" (ablution) or "Afahye" (public festival), are therefore celebrated each year on different days of the year. The priests of the various gods, in consultation with the various gods and ancestors, determine which Adaduanan cycle to choose for the annual rites, usually depending upon the ripening of the crops. Any series of annual rites is observed on the same days of the Adaduanan each year, although not on the same days of the year as reckoned by the Gregorian calendar.
Months.
The various Adaduanan cycles within the year are given a number of appellations, which are not the same from place to place, and of course never quite the same from year to year, since there are fewer than nine and more than eight cycles in any one year. "OpƐpon" ("OpƐ", harmatan, dry season; "pon", supreme) for example, more or less corresponds to the Adaduanan which appears about January–February in the middle of the dry season. Every three years or so, one of the nine named Adaduanan is omitted from the year because of the extra thirteen days gained when observing nine cycles a year. The names of the Adaduanan are therefore flexible and vary over time and cline.
Today some of the names for the Adaduanan cycles have been arbitrarily applied to the Gregorian calendar of twelve months by some Akan scholars, although there is no traditional basis for such a translation. For example, "Opepon" is now used for the Akan word for January even though in the traditional Akan calendar there is no concept exactly corresponding to the Roman month of January (Janus the god facing the past and future). The beginning and end of each Akan year tends to be the various yam festivals celebrated around August or September.
Lunar Month.
The lunar cycle and 28-day month are not carefully observed, except by the coastal Akan who are interested in tides as they affect fishing. Still, the month is known as "bosome". It consists of 28 days rather than the 30 or 31 days of the Gregorian calendar. Three "bosome" make two Adaduanan. Since the arrival of Swiss missionaries from Basel in the early nineteenth century, Christian Akan scholars have tended to 'Akanize' the Roman calendar rather than observe, analyse and explain the Akan calendar based on Adaduanan.
Gregorian Calendar.
It is quite easy to calculate the Akan calendar from the Gregorian calendar once a few keys are known. Understandably there is no equivalent in English to the six-day week. The seven-day week of the English and Akan calendars are, however, equivalent, with the suffix "-da" (day) added to the names of the days in the above list (Sunday is "Kwasida", Saturday is "Memenada", and so on). Every second year or so Easter occurs on an "Akwasidae". In 1978, there are nine "Akwasidae", celebrated on 8 January, 19 February, 2 March, 14 May, 25 June, 30 July, 6 August, 17 September, 29 October and 10 December, that is every sixth Sunday. The first four "dabɔne" of 1978 were "Akwasidae" (8 January), "Fodwo" (23 January), "Awukudae" (1 February), and "Fofi" (10 February). Other "dabɔne" may be calculated infinitely from these by adding or subtracting six-week intervals.
The synthesis of a six-day week and a seven-day week, forming the 42-day Adaduanan cycle may be added to numerous other items of evidence to support a theory of the origins and development of Akan culture which suggests that it is based on cultural diffusion and a compromise of observances having diverse origins.