This score was written in the years prior to 1943, when it was published and officially released to the public. There’s no real information about when music is written aside from when it is published, so this is the best answer one can give to this question. It was the first work of the composer, Samuel Barber.
He was born in 1910, and died in 1981 at the age of 71. He’s one of the few American composers to have acclaim early in his career, and to have that acclaim last through his career and beyond his death. Many famous composers with this kind of fame are German, Austrian, etc. He played the piano and the violin, and composed for operas and orchestras.