Closest approach is near the time the planet reaches opposition.
At opposition, a planet lies opposite the Sun in Earth's sky. The planet rises at sunset, reaches its highest point in the sky at midnight, and sets at dawn. Saturn comes to opposition on Sunday, November 19, and Jupiter comes to opposition on Monday, November 27. If you envision the solar system as a giant race track, Earth is moving in an inner lane. Jupiter and Saturn come to opposition when the faster moving Earth overtakes and passes the outer planets.