There are actually a few examples for using the Genitive: eines Morgens, eines Mittags, eines Abends, eines Nachts. The latter may seem confusing because it is die Nacht. However, des Nachts or eines Nachts is a collocation and requires masculine gender for a reason I don't know. The given examples are not very common in spoken language though. But I should think they are still quite commonly used in narrations. The term "eines Tages" is used both in narrations and common language. In common language usually when speaking about the future and giving sort of warnings or prophecies or even threatening someone. Eines Tages wirst du erkennen, dass du hier im Unrecht warst. Eines Tages wirst du das bereuen. Eines Tages wird dir das noch leid tun!

@ Stefano thank you! That is indeed a very clear and useful article!

I found an article in Internet regarding the use of accusative and genitive to express time. Here is the link: http://www.dartmouth.edu/~deutsch/Grammatik/Zeit/Time.html 1) Definite Time -> accusative; 2) Indefinite Time -> genitive.