This is a line from "Der Vorleser" by Bernhard Schlink:
Eines frühen Abends im Februar hörte ich eine Amsel singen.
One early evening in February I heard a blackbird singing.
Why is the eines in the genitive? "One" is not belonging to anything.
Why isn't it like this:
einer frühen Abends
This is a sentence from one of my textbooks:
einer meiner Handschuhe fehlt
one of my gloves is missing
The "einer" in this sentence in masculine and nominative.
--- EDIT ---
Thanks for the help. I was confusing the pronoun "einer" meaning "one of" with the article "ein" meaning "a" or "one".