This film is set during the fall of 1928 and the spring of 1929. You know this because when they celebrate new years eve, after the stroke of midnight, Lisa states that "it's 1929 now". All clothes are from the 1920s except for those especially made for the movie. They, however, where made from cloth from the 1920s. This annoyed the child actors since that kind of cloth is very itchy.
The village where the Bullerby movies were recorded is called Sevedstorp. During the summer more than 2,000 people pass the village every day to see the three famous houses where all the characters live in the movies.
Stand-ins for the six children were cast from a local school. This was made in order to save time so some shoots could be taken without the main actors. However, there was no girl tall enough to stand in for Ellen Demérus, so a boy named Anders Jonsson was cast instead. According to his sister, who is an extra in the film, you can see that it's not a real girl because Anders doesn't walk or run like one.
This movie and its prequel (Alla vi barn i Bullerbyn (1986)) were shot back to back and it begins at the same moment that the other one ends (the last thing you see of the six children in the last film is that they leave the Bullerby village to go to school on the first day after the summer holidays, and the first thing you see of them in this one is their walk to school on the same day).