1989: Whew! That was close! An asteroid measuring an estimated 300 metres across, travelling at 74,000 km/h, came within six hours of slamming into the Earth. The asteroid, named Asclepius, crossed Earth’s orbit and passed within 650,000 kilometres of the planet. A collision with an object of that size, moving at that speed, would have seriously rattled the crockery.
Source: Gerrit L. Verschuur, Impact!: The Threat of Comets and Asteroids (1996), p. 116