Location: Austria, Vienna, Ottakring Forest
Time: 2019, Feb 2, 16:02 local time
I found many tree stumps nearby covered by moss, but only this one displaying the fungi. I am not knowledgeable enough to determine the species of the tree.
I first suspected a Ganoderma, but none of the species listed on Wikipedia looked very similar.
A better bet might be Lenzites Betulina although the pics on Wikipedia always seem more richly coloured than mine. You can check many pics of L. Betulina candidates on mushroom observer. The L. Betulina in this Video also seem to have more marked rings.
Edit: After some searching I am also considering Trametes Pubescens, as Wikipedia remarks:
Unlike most other turkey tail-like species of Trametes, the cap surface lacks strongly contrasting zones of color.