Green’s Dictionary of Slang

sex in the afternoon.

1976		Starland Vocal Band ‘Afternoon delight’ 🎵 Gonna find my baby, gonna hold her tight / Gonna grab some afternoon delight.
1985		‘Thommo’ Dict. Aus. Swearing & Sex Sayings 11: AFTERNOON DELIGHT—Sexual intercourse during the afternoon. Usually an “on the spur” of the moment decision, either at the office, on a country picnic, on a deserted beach, or anywhere your sexual desire feels the need to be satisfied.
1988		Billboard Book of Number One Hits 🌐 The Danoffs thought they might have had a problem getting airplay on ‘Afternoon Delight,’ but few stations found it objectionable. ‘If the song had been banned it would have been a real injustice.’.
1999		Youth Outlook (CA) 1 Oct. [headline] Afternoon Delight or Always and Forever?
2010		H. Freeman in Guardian 1 Nov. 🌐 Nobody needs to see your cleavage, with the exception of Mrs Barry on special nights, and maybe the occasional afternoon delight.