Which unit has the difference of two Date.now() calls?

Reference say: "Get the number of milliseconds" So the difference should be micro seconds.

why milli-milli=micro?

Not shure because a output of Date.now() looks like this 41866529.26635742187.

Still it can be milli but with fraction

BTW there is also getTime() - similar but in seconds with fraction

EDIT: what is a bit strange is that in Bangle 2 emulator Date.now() has no fraction