Lowery recalls that the Daleks invaded Earth 1,000 years earlier, which was established as having taken place in or before 2164 in World's End (1964). It was later established in The Nightmare Begins (1965) that this episode took place in 4000. As such, the Dalek invasion of Earth was more than 1,800 years earlier.
The terms "solar system," "galaxy" and "universe" are used interchangeably.
Marc Cory learns of the Daleks' secret plan to conquer the galaxy when he overhears it on the loudspeaker in the Dalek city.