Many People over the last 100 years have sung "Happy Birthday to You"
not knowing the history of the song.
Here is what one researcher pieced together.
A woman named Mildred Hill from Louisville, Kentucky USA wrote the tune in 1893.
Her sister provided lyrics and the song was published under their name.
In 1924 without their permission a man named Robert Coleman
added the lyrics we use today. The Hill family sued him and won an
exclusive copyright. This Copyright was later sold to Warner Communications.

Almost no birthday celebration is held without singing this song and the lyrics without the tune have graced countless birthday cards.

In 2002 the Mayor of Louisville dedicated a parking lot to them with
a marker telling the story of how the song began. The city calls the place the "Happy Birthday Lot"

while we are on the subject of Birthdays, a couple more references might be in order.
First the List of birthdays at A293195 then the quest for a new song or
songs at A663815.