"Tuupaapaku are seen as things of the night, yet also perhaps of particular nights. The pattern of spirit actions is linked with the arapoo, the 'path of the nights' of the traditional lunar calendar. Few Cook Islanders could now provide a full listing of the arapoo, the named nights of the lunar calendar.

Nevertheless, particular pieces of knowledge connected with the lunar calendar are still used in activities such as planting, fishing, and crab collecting, and the links between specific nights and spirit appearances are sufficiently strong in some minds for the term arapoo to be applied to both.

Three nights strongly linked with ghosts are those with the name Rakau, usually said to be the eighteenth, nineteenth, and twentieth after the new moon, when the moon is beginning to wane.

In Atiuan tradition... the first of these, Rakau ta'i, is a night 'when spirits arise to reenact their past and remind us that they are still there'.

According to a listing of arapoo published in the Cook Island journal Torea Katorika the subsequent nights are:

19 Rakau roto - Po ika kore. Maataa te turuma i roto i te tai.

Rakau roto - Night of no fish. Many apparitions in the sea.
20 Rakau akaoti - Kua aere te turuma ki runga i te maunga.

Rakau akaoti - The spirits go inland to the hills/mountains."

(Oral Traditions)