The trailer opens with Billie talking about her struggle dealing with all kinds of transitions.
Billie walks in on her father wrapping his chest.
Billie and her father talk with a doctor about what will happen during her father's transition.
Then, there's a moving montage of clips as Billie keeps repeating the word "Dad."
Meanwhile Billie is trying to figure out who she is as a 16-year-old.
The father is played by Del Herbert-Jane, a gender non-conforming actor who is not trans, but welcomed the character.
The film's star, Tilda Cobham-Hervery, had never been in a film before.
Billie only sees her father on Tuesdays while her father transitions, so the director only filmed the movie on Tuesdays over the course of a year.
The director, Sophie Hyde, won the best directing award for the film in the World Cinema Dramatic category at the 2014 Sundance Film Festival this past January.
The film launched a global project with an app called "My 52 Tuesdays" where the film asks a question every Tuesday and users submit an image of themselves holding their response on a piece of paper.
The film comes out in Australian cinemas on May 1st, 2014.
