We've included two versions below. The first is by the great Irish folk singer Liam Clancy whom Bob Dylan considered "...the best ballad singer I'd ever heard...". Liam Clancy and Gene Raskin were friends and drinking buddies.
The second version is the one that is best remembered. It's the 1968 recording by Welsh singer Mary Hopkin, produced by Paul McCartney, which became a major hit in the US and the UK. There's accompanying lyrics in this version, so you can sing along and reminisce about YOUR good old days.