William J. Thomson, paymaster on the USS Mohican, spent twelve days on Easter Island from 1886, 19 December to 30 December. Among the data Thomson collected were the names of the nights of the lunar month and of the months of the year:[1]
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.
The months
Thomson recorded the months as follows:
Rapanui name
Meaning
Western equivalent, 1886-1887
Anekena
August
Hora-iti
little summer
September
Hora-nui
big summer
October
Tangarouri
part of November
Kotuti
November and December
Ruti
December and January
Koro
January
Tuaharo
February
Tetuupu
March
Tarahao
April
Vaitu-nui
big winter
May
Vaitu-poto
short winter
June
Maro or Temaro
July
The days
The Mamari Tablet of rongorongo is thought to include the Rapanui calendar. The identified calendrical information starts midway through recto line 6 (bottom center, upside down) and continues to the start of line 9 (top left). Two glyphs completing the purple sequence (elipsis) are not visible at the start of 7. Blue and pink beaded lozenges ("accounting sets") follow the identified calendar, but their function is unknown.
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;[2] Thompson records the crescent was first visible on Nov. 26.
Rapanui name
Meaning
Western equivalent, 1886
Kokore tahi
first kokore
November 27
Kokore rua
second kokore
November 28
Kokore toru
third kokore
November 29
Kokore hâ
fourth kokore
November 30
Kokore rima
fifth kokore
December 1
Kokore ono
sixth kokore
December 2
Maharu
first quarter
December 3
Ohua
December 4
Otua
December 5
Ohotu
December 6
Maure
December 7
Ina-ira
December 8
Rakau
December 9
Omotohi
full moon
December 10
Kokore tahi
first kokore
December 11
Kokore rua
second kokore
December 12
Kokore toru
third kokore
December 13
Kokore hâ
fourth kokore
December 14
Kokore rima
fifth kokore
December 15
Tapume
December 16
Matua
December 17
Orongo
first quarter [sic]
December 18
Orongo taane
December 19
Mauri nui
December 20
Marui [sic] kero
December 21
Omutu
December 22
Tueo
December 23
Oata
new moon
December 24
Oari
December 25
Kokore tahi
first kokore
December 26
The three sources we have 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:
day
Englert
Thomson
Métraux
day
Englert
Thomson
Métraux
*1
oata
oata
ata
*15
omotohi
omotohi
motohi
2
ohiro
oari
ari
16
kokore tahi
kokore tahi
kokore tahi
3
kokore tahi
kokore tahi
kokore tahi
17
kokore rua
kokore rua
kokore rua
4
kokore rua
kokore rua
kokore rua
18
kokore toru
kokore toru
kokore toru
5
kokore toru
kokore toru
kokore toru
19
kokore hâ
kokore ha
kokore ha
6
kokore hâ
kokore ha
kokore ha
20
kokore rima
kokore rima
kokore rima
7
kokore rima
kokore rima
kokore rima
21
tapume
tapume
tapume
8
kokore ono
kokore ono
kokore ono
22
matua
matua
matua
*9
maharu
maharu
maharu
*23
orongo
orongo
rongo
10
ohua
ohua
hua
24
orongo taane
orongo tane
rongo tane
11
otua
otua
atua
25
mauri nui
mauri nui
mauri nui
x
—
ohotu
hotu
26
mauri karo
mauri kero
mauri kero
12
maure
maure
maure
27
omutu
omutu
mutu
13
ina-ira
ina-ira
ina-ira
28
tireo
tireo
tireo
14
rakau
rakau
rakau
x
—
—
hiro
*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 kokore is cognate with Hawaiian ‘a‘ole "no" and Tahitian ‘aore "there is/are not"; here it may mean "without [a name], nameless".[1]
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.[3]
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.[4]
However, Guy[5] 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.[6]
References
^ THOMSON, William J. 1891, p546. "Te Pito te Henua, or Easter Island". Report of the United States National Museum for the Year Ending June 30, 1889. Annual Reports of the Smithsonian Institution for 1889. 447-552. Washington: Smithsonian Institution. (An online version is available [www.sacred-texts.com/pac/ei/ei61.htm here])
^ Calculated here. Easter Island is about 109° (7.3 hours) west of Greenwich Mean Time, so the 9:55 AM UTC new moon of Dec. 25 occurred at 2:38 AM local time, on the night of Dec. 24.
^ MÉTRAUX, Alfred. 1940, p52. "Ethnology of Easter Island." Bernice P. Bishop Museum Bulletin 160. Honolulu: Bernice P. Bishop Museum Press.
^ BARTHEL, Thomas S. 1978, p48. The Eighth Land. Honolulu: the University Press of Hawaii.
^ GUY, Jacques B.M. 1992. "À propos des mois de l'ancien calendrier pascuan" ("On the months of the old Easter Island calendar"), Journal de la Société des Océanistes 94-1:119-125
^ 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.