About how many Earth days is Venus’s synodic period as seen from Earth? Venus’s synodic period is about 584 Earth days.
A synodic period is the time between successive similar configurations of a planet as viewed from Earth—for example, from one greatest eastern elongation to the next, or between corresponding appearances in the sky. It is not the same as the planet’s orbital period around the Sun.
Venus completes one orbit in about 224.7 Earth days, but Earth is moving around the Sun at the same time. Because both planets are in motion, Earth must “catch up” to Venus before the same apparent alignment repeats. That relative motion produces the roughly 584-day cycle.
This cycle helps explain why Venus alternates between being a prominent morning star and evening star. Venus can never appear far from the Sun in our sky, because its orbit lies inside Earth’s orbit. Its synodic period is therefore a useful concept for understanding its changing visibility, while its 225-day orbital period describes its year.