When Does "The Sound of Music" (1959) Take Place?

"The Sound of Music" is a historical fiction stage musical written by Howard Lindsay with Russel Crouse, Richard Rodgers, and Oscar Hammerstein II and released November 16th, 1959. 

It takes place in the years: 

1926 AD - 1938 AD 

We know this because it tells the story of the real-world bandleader Maria von Trapp and by the beginning of the fourth song, "Do-re-Mi", she's just met the von Trapp family for the first time and that happened in the real world in 1926 AD. 

Near the musical's end, during the fifteenth song, "Processional", we are shown Maria's marriage to the real-world Austrian submarine commander Georg Ludwig von Trapp which happened in the real world on November 26th, 1927 AD. 

Then, Adolf Hitler's Nazi Germany invades and annexes Austria during their month-long honeymoon vacation. In the real world, the Anschluss (as the quasi-legal annexation was called) started on March 12th, 1938 AD. (This impending calamity is discussed in the thirteenth song, "No Way to Stop It", very early in act 2.) 

Soon after, the whole von Trapp family competes in the real-world Salzburger Festspiele, (the Salzburg music festival; 1877-present). HOWEVER, this all actually happened earlier in the real world, in 1936 AD. In the story, this is when Georg performs the eighteenth sing, "Edelweiss", and the children sing a reprise of "So Long, Farewell" as the nineteenth song. 

Finally, the musical makes this all nearly simultaneous with the family fleeing for a nearby country, during the twentieth and last song, a reprise of "Climb Ev'ry Mountain", which happened in June of 1938 AD in the real world. 

This Prologue magazine article by Joan Gearin examines its exact setting. 

There was a London revival in 1961, then another in 1981, and again in 2006, an Austrian revival in 2005, and a Broadway revival in 1998. 

It was adapted to film in 1965 and to television in 2013.