"Who Knows Where the Time Goes?" is a song written by the English folk-rock singer and songwriter Sandy Denny. People commonly think that the recording by Fairport Convention is the original one.

1967 Sandy Denny recorded the song with voice and guitar as a demo.
1967 Later that year, she briefly joined the folk band The Strawbs and re-recorded the song, again with only her voice and guitar. This was eventually released on the album All Our Own Work in 1973.
1968 Judy Collins heard a tape of the original demo recording and decided to cover the song. She released the first version with vocal, two guitars, and bass on the B-side of "Both Sides Now" (released October 1968).
A second version appeared on the album Who Knows Where the Time Goes? (released November 1968). The first verse is the same take as the first version, but with everything remixed to the left channel, then crossfading to a different recording with a larger arrangement, modulated to different key. Acoustic Guitar – Judy Collins; Acoustic Guitar, Electric Guitar – Steven Stills; Drums – James Gordon; Electric Bass – Chris Ethridge; Piano – Michael Sahl. This was the first widely available recording of the song.
1968 Sandy Denny joined the folk-rock band Fairport Convention.
1969 She recorded the song on her second album with the band, Unhalfbricking. Recorded: January–April 1969. Released: 3 July 1969. This version had more of a rock influence.
2007 The Unhalfbricking version was voted "Favourite Folk Track Of All Time" by listeners of BBC Radio 2.
Information from Wikipedia and Discogs.