Q. Is George Gershwin's song "Summertime" a public domain composition?
A. No "Summertime" is not a public domain composition at this time anywhere.
"Summertime" is an aria composed by George Gershwin for the 1935 opera Porgy and Bess. The lyrics are by DuBose Heyward, the author of the novel Porgy on which the opera was based, although the song is also co-credited to Ira Gershwin by ASCAP. Ira Gershwin died on 17th August 1983 and his works are therefore in copyright throughout the world (USA excepted - please see below) until 2053.
Under the "Sonny Bono" Copyright Extension Act, this work would be in copyright in the USA through 2018 even if Ira Gershwin were not involved.
So, the song will become a public domain composition in the US starting in 2019, and elsewhere in the world in 2053.
In the mean time, the song can be licensed via Warner Chappell. For more information, click here to visit the ASCAP web site with publisher contact information.