Story of happy birth day song

In 1983 two American sister's, who wre teachers, wrote this song to sing in school assmbiles. Milder j. and patty Smith Hill orignally called the song "Good morning to you". After this word were changed in 1924, it become to world ower. the song will be copyright untel 2030, but only for commercial puposes.Singing it at a bithday party does not infringe copyright!