Shadow period

The pre-shadow begins the moment a planet first reaches the degree it will later station direct at, well before the retrograde itself starts; the post-shadow doesn't end until the planet, moving forward again, finally passes the degree it originally stationed retrograde at. Across the whole shadow, the planet covers the same narrow stretch of the zodiac three separate times: once moving forward, once moving backward, once moving forward again. Effects associated with a retrograde are often felt loosening in during the pre-shadow and settling fully only once the post-shadow clears, rather than starting and stopping cleanly on the two station dates alone. Mercury's shadow periods are the ones tracked most closely on this site, since they bracket its retrograde windows by a few extra weeks on either side.