Valentin Gaft ( Pavel Ikonnikov in the movie) was 7 when WW2 Siege of Leningrad happened, so he clearly can't be adult musician who was sent by government to entertain troops (as his wife told in the movie). Movies was shot in 1987 (ans set in 1987), book on which films is based is released in 1972 - creators just forgot to change time line in the movie.