“Contemporaneous” vs “simultaneous”

Question

I've done a bit of searching but cannot find a definitive distinction between contemporaneous and simultaneous. I personally use the words interchangeably. Am I correct in doing so?

Answer 1

The OED gives these definitions, which look pretty typical to me:

Contemporaneous: Belonging to the same time or period; existing or occurring at the same time.

Simultaneous: Existing, happening, occurring, operating, etc., at the same time; coincident in time.

So "contemporaneous" refers to things that happened in, or are associated with, the same period of time, whereas "simultaneous" refers to things that happened at the same moment.

To put it another way, contemporaneous things were happening at the same time, while simultaneous things happened at the same time.

Answer 2

Contemporaneous implies things happening during broadly the same period of time. Simultaneous conveys a greater sense of things happening at exactly the same time.