Where & When
The story is set on the planet Skaro. The few stories that have attempted to give any hint as to where this might be in relation to Earth generally place it in a different galaxy but all we can say with certainty is that it’s a long way away.
Since the story, taken on its own terms, has no connection with Earth, the date is equally impossible to determine. As one might expect, multiple different theories have been advanced, some placing it very early in Dalek history, before they developed space flight, others in the far future, when a forgotten and degenerate group have been left behind on their home planet, cut off from their fellows. Most go for somewhere in between, often one or two centuries into our future, but it's probably more accurate to say that we just don’t know.