Ian Gillan has said that "Child in Time" is based on It's a Beautiful Day's psychedelic song "Bombay Calling". It's a Beautiful Day in return borrowed Purple's "Wring That Neck" and turned it into "Don and Dewey" on their second album Marrying Maiden (1970). As Ian Gillan put it in a 2002 interview, "There are two sides to that song - the musical side and the lyrical side. On the musical side, there used to be this song 'Bombay Calling' by a band called It's A Beautiful Day. It was fresh and original, when Jon was one day playing it on his keyboard. It sounded good, and we thought we'd play around with it, change it a bit and do something new keeping that as a base. But then, I had never heard the original 'Bombay Calling'. So, we created this song using the Cold War as the theme, and wrote the lines 'Sweet child in time, you'll see the line.' That's how the lyrical side came in. Then, Jon had the keyboard parts ready and Ritchie had the guitar parts ready. The song basically reflected the mood of the moment, and that's why it became so popular."
"Child in Time" is one of the last tracks on which Blackmore recorded his parts using the Gibson ES-335 that had been his mainstay electric instrument in Deep Purple's early years prior to switching to Fender Stratocasters.
A staple of the Deep Purple live concerts in 1970–73 and later after their initial reunion tours of 1985 and 1987–88, the song was not featured regularly at concerts after 1995. It was re-added to the setlist for the band's 2002 European tour, with its final appearance in Deep Purple's live set was at Kharkiv's Opera Theatre's scene in March of that year.
A live version later appeared on the 1972 live album Made in Japan. Another live version can be found on the Scandinavian Nights / Live in Stockholm live album, recorded in September 1970. Gillan also featured a live jazz influenced version of the song in his Ian Gillan Band project of the late 1970s.