When was Shostakovich's historical period?

Shostakovich lived his whole life during the 20th Century. His oeuvre is thus classified as 20th Century classical music. However, Shostakovich's compositions also often display an affinity with the Romantic classical music tradition, and in general his scores shy away from the extreme experimental nature characteristic of the 20th Century idiom, although towards the end of his life Shostakovich began to incorporate serialism into his music.