The only "current" example of this is Africa/Casablanca (Morocco).
There's a good visualization here:
-Matt
At
this stage I haven't continued on my search for a quad-change locality
(I'll
wait till I better understand the 'simple' ones, such as the above,
first!),
but if anyone can direct me to a quad-change rule, it would save me
some
time further down the track.