Quoc: "What a Diff'rence a Day Made", also recorded as "What a Diff'rence a Day Makes", is a popular song originally written in Spanish by Maria Grever, a Mexican songwriter, in 1934 with the title "Cuando vuelva a tu lado" ("When I Return to Your Side"). The song is also known in English as "What a Diff'rence a Day Makes", as popularized by Dinah Washington.

Who sang what a difference a day makes first?
HW Chung: OK, some thoughts:
The relevant information to answer the above question is: "What a Diff'rence a Day Made", also recorded as "What a Diff'rence a Day Makes", is a popular song originally written in Spanish by Maria Grever, a Mexican songwriter, in 1934 with the title "Cuando vuelva a tu lado" ("When I Return to Your Side"). The answer is Maria Grever.