T39484 raised that timeline frame range representation actually show (real_length - 1) interval… So e.g. a scene having same start and end frame is shown as zero length. This is also inconsistent with how caches are drawn in same window (they start at -0.5 frame and end at +0.5 frame), which allows to represent the real length, assuming 'frame' itself as a sort of “center” value.
To fix T39484 I simply made same thing for frame range, but this was to quick in fact, we need a design decision here and make it consistent in all time-related windows (timeline, VSE, MCE, animations, etc.).
@Sebastian Koenig (sebastian_k) proposed to rather draw a [start, end+1] interval, adding a small green square of one frame width to the cursor: