The comet with the longest period that has been seen to return to the inner Solar System. Discovered in 1661, when it was extensively observed by J. Hevelius, it returned to perihelion in 2002 and was independently rediscovered by the amateur astronomers Kaoru Ikeya (1943– ) of Japan and Zhang Daqing (1969– ) of China. Currently it has a period of 366 years, perihelion 0.507 au, aphelion 101.9 au, eccentricity 0.990, and inclination 28°.1.

http://cometography.com/pcomets/153p.html Information page at Cometography website.