When Does the Film "The Sound of Music" (1965) Take Place?

"The Sound of Music" is a historical fiction film musical written by Ernest Lehman and Robert Wise [adapting "The Sound of Music" (1959) b Howard Lindsay with Russel Crouse, Richard Rodgers, and Oscar Hammerstein II] and released March 2nd, 1965. 

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, after an opening montage of the landscape and the first musical number, the movie includes a time and place setting title card reading, "Salzburg, Austria, in the last Golden Days of the Thirties". 

HOWEVER, the beginning of the story introduces Maria to the von Trapp family for the first time and this happened in the real world in 1926 AD. 

At about three-quarters through the film, we are shown Maria's marriage to the real-world Austrian submarine commander Georg 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. 

Soon after, the whole von Trapp family competes in the real-world Salzburger Festspiele, (the Salzburg music festival; 1877-present). HOWEVER, this actually happened earlier in the real world, in 1936 AD. 

Finally, in the film, this is all made nearly simultaneous with the family fleeing for a nearby country, which happened in June of 1938 AD in the real world. 

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