Daybill posters are generally sized 13" x 30" or 33cm x 77cm, although this can vary slightly depending on year and studio. In the late 80s, this size shrunk to 13" x 26" /33cm x 66cm.
Australian One Sheets typically measure 27" x 41" / 68cm x 104cm pre 1985, or 27" x 40" / 68cm x 100cm post 1985.