The glyph type ihe tau appears at the close of calendars, or at the end of main sections of calendars.

The picture is that of a moon crescent broken in half, which conveys suggestions of a time when growing no longer continues - i.e. a state of death. If ihe tau is reversed, it becomes a sign of birth, as at right in Ab1-37:

South of the equator the crescent of a waxing moon looks reversed as compared to how it is seen north of the equator. Therefore the half moon in ihe tau represents half a waning moon. In Ca7-27, beyond full moon in the Mamari moon calendar, an unusual variant of marama (moon) describes waning moon as a waxing moon crescent turned around 180º:

The light part has become the bottom and the dark (hatchmarked) part has come to the top. The glyph presumably illustrates how the waxing moon has 'broken'.

A few notes regarding the structure of Mamari (C).