What Day, Which Day
Expression
なんにち
何日仕ごとを休んでいたんですか。
How many days of work were you taking off?
何日がごつごうよろしいですか？
What day would be good for you?
あなたはその島から何日間出られなかったんですか？
How many days were you stuck on that island?
What day equals the fairly obvious translation "what day." But, it also means how many days.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.