There is no guarantee code ported from Wikipedia will work on FANDOM, especially Lua. You might get better answers at Scribunto Help board on the Dev wiki. They have experts there that helped set up the Lua functionality on FANDOM and may see the problem immediately.
if module says "invalid date", then you probably supplied invalid date. according to the module, you are using it by wrong way: the module waits y, m and d as 3 different params. it would be much better to read the documentation, i believe that wikipedia have one.
While it does work like that, it is also meant to work with yyyy-mm-dd in one as well. That is how it was used on Wikipedia and worked. If we can't find out how then I will indeed edit the lists to use the different params menthod instead.