The Rapa Nui calendar was the indigenous lunisolar calendar of Easter Island. It is now obsolete.

Attestation

William J. Thomson, paymaster on the USS ''Mohican'', spent twelve days on Easter Island from December 19 to 30, 1886. Among the data Thomson collected were the names of the nights of the lunar month and of the months of the year: :''The natives reckoned their time, and in fact do so still by moons or months, commencing the year with August, which was, according to the traditions,the time when Hotu-Matua and his followers landed upon the island.''

Months

Thomson recorded the months as follows: :

Days

The month was divided in two, beginning with the new and full moon. Thomson recorded the calendar at the time of his visit to the island as follows. The new moon occurred on November 25 and again on the night of December 24; Thompson records the crescent was first visible on November 26. : Three sources correspond with each other except for two intercalary days (in bold), and the night of the new moon in Englert, which seems to have been confused with one of these. Beginning with ''(o)ata,'' the night of the new moon, they are: :*New moon, full moon, and first and last quarters. The ''kokore'' are unnamed (though numbered) nights; ''tahi, rua, toru, haa, rima, ono'' are the numerals 1–6. The word is

cognate In historical linguistics, cognates or lexical cognates are sets of words that have been inherited in direct descent from an etymological ancestor in a common parent language. Because language change can have radical effects on both the s ...

with Hawaiian ''‘a‘ole'' "no" and Maori ''kahore'' "no" and Tahitian ''‘aore'' "there is/are not"; here it may mean "without name nameless

The word ''kokore'' is cognate in other Polynesian calendars such as the series of nights called ''korekore'' in the calendars found in New Zealand.

Analysis

The calendar collected by Thomson is notable in that it contains thirteen months. All other authors mention only twelve, and Métraux and Barthel find fault with Thomson: :''Thomson translates Anakena as August and suggests that the year began at that time because Hotu-Matua landed at Anakena in that month, but my informants and Roussel (1869) give Anakena as July.'' :''We are basing the substitution on the lists by Metraux and Englert (ME:51; HM:310), which are in agreement. Thomson's list is off by one month.'' However, Guy calculated the dates of the new moon for years 1885 to 1887 and showed that Thomson's list fit the phases of the moon for 1886. He concluded that the ancient Rapanui used a lunisolar calendar with ''kotuti'' its embolismic month (AKA "leap month"), and that Thomson chanced to land on Easter Island in a year with a leap month. The days ''hotu'' and ''hiro'' appear to be intercalary. A 28-day calendar month needs one to two intercalary days to keep in phase with the 29½-day lunar month. One of the rongorongo tablets may describe a rule for when to add these days.GUY, Jacques B.M. 2001. "Le calendrier de la tablette Mamari", ''Bulletin du Centre d'Études sur l'Île de Pâques et la Polynésie'' 47:1–4.

References

{{Calendars Easter Island Specific calendars Rongorongo