Overview
This song has no relation to the song traditionally sung on people's birthdays.
"Happy Birthday" is a song written, produced and performed by Stevie Wonder for the Motown label. Wonder, a social activist, was one of the main figures in the campaign to have the birthday of Martin Luther King Jr. become a national holiday, and created this single to promulgate the cause. The song has since become a standard for use during birthdays in general, particularly among African-Americans.
"Happy Birthday" was released as the fourth single of Wonder's Hotter than July (1980) album in June 1981. It was one of his most popular entries in the UK Singles Chart. It was not released in the United States, but is still regarded as one of his signature songs.
Background
The song, one of many of Wonder's songs to feature the use of a keyboard synthesizer, features Wonder lamenting the fact that anyone would oppose the idea of a Dr. King holiday, where "peace is celebrated throughout the world" and singing to King in the chorus, "Happy birthday to you". The holiday, he proposes, would facilitate the realization of Dr. King's dreams of integration and "love and unity for all of God's children".
From Wikipedia (CC BY-SA 4.0).