Original: Voyager 1s Saturnian flyby occurred in November 1980, with the closest approach on November 12, 1980, when the space probe came within 124000 k of Saturn's cloud-tops.
Simplified: Voyager 1s Saturn flyby occurred in November 1980, with the closest approach on November 12 when it came within 124,000 kilometers (77,000 miles) of the planet's cloud-tops.