Here I find it useful to include my thoughts about GD34 (kava). A change of state is the message conveyed by this typ of glyph. Thinking about this 'snake' at dawn it is clear that the change of state is from night to day, thinking about spring equinox the change is from winter to summer, thinking about birth the change is from inside (darkness) to outside (light).

"... on the spring and autumn equinoxes, regular as clockwork, triangular patterns of light and shadow combined to create the illusion of a giant serpent undulating on the northern staircase ..."

I guess, though, that it was just at dawn/birth/spring equinox that the snake was there in the minds of the observers. In the evening/at death/autumn equinox, the play of light and dark may have been objectively similar, but they had another flavour:

"... the new moon appears in the west, the full moon rides in the south, the waning moon is in the east, and to the north there is no visible moon ..."

"This lunar order may also be considered a solar order if the annual, not the daily , movement of the sun is considered. For the points of rising and setting of the sun move E N W S. After rising due east at the spring equinox it rises more northerly as summer goes on, sinks then due west at the autumnal equinox, and then sets more southerly until the winter solstice is reached. This motion (W [wood] w [water] M [metal] F [fire] in terms of the elements) becomes therefore a special case of the lunar sequences." (Needham II)

So the moon is born at sunset, where the crest of the wave is sinking down. But I have seen the moon in all is phases all over the sky - I even remember a full moon in the north. However, if there be order, then moon, darkness, death, winter, disorder etc must be born in the west.