Last Quarter
About half of the visible lunar disk is illuminated while the Moon is roughly 90 degrees west of the Sun.
Astronomy
About half of the visible lunar disk is illuminated while the Moon is roughly 90 degrees west of the Sun. Phase boundaries in an eight-part model are conventions applied to a continuous change in lunar illumination.
Modern symbolic interpretation
Often framed as a symbolic checkpoint for revision, release, and deliberate course correction.
This is an interpretive convention rather than a measured physical influence on human events.