What Year
How Many Years
noun
You have the kanji what and year, as in: "what year is it?"
This also means how many years too, depending on the context. As in: "How many years did you play soccer?"
なんねん
The readings are both the readings you learned with the separate kanji, meaning you should know them. How many years have you been studying kanji now? You should be able to read this one.
何年生まれですか。
What year were you born?
おたくのお子さんは、何年に大学に入りましたか。
What year did your kid enter college?
アメリカの南北戦争は、何年間続いたんですか？
How many years did the American Civil War last?