Beyond autumn equinox sun is 'absent' and the number of glyphs should no longer be 28 for a group of periods. Instead, the season can be expressed by way of 29 glyphs. 29 symbolizes the 29th dark moonless night which follows the 28 nights when moon is at least potentially visible. Likewise, the darkness following autumn equinox resembles a moonless night - it is a 'sunless night'.

'Waning moon' (to change metaphor) is the time when the power of the moon subsides, which implies that the power of the sun must increase to compensate for the loss. The concept can be expressed by way of counting 30 + 6 = 36 over a group of 10 periods (24-0).

The imagined structure has 7 periods for the moon (17-23) and 16 (1-16) + 10 = 26 periods for the sun. There are 3 groups of periods for the moon and 6 + 4 = 10 for the sun.

The 17th period is the first of the moon periods, while the 16th (or rather 26th) is the last of the sun's. The last sun period is single (not belonging in a group with other periods) and as if in a mirror the first moon period is also single.

121 is not a random number, it can be explained as 4 times 10 + 4 times 13 + 29. The sum of 10 and 13 equals the number 23 of the last 'black' period in the calendar. There are 13 * 28 = 364 days in a lunar calendar for the year, and 10 was the old traditional number of months in Polynesia. The number of glyphs in period 16 (i.e. the 26th and last sun period) has been reconstructed as 13.