Midnight
Twelve O'clock
noun
Zero o'clock is 0:00. That's midnight or twelve o'clock.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
零時頃、彼女が町中を一人で猛スピードで歩いているのを見かけました。
I saw her walking really fast downtown by herself around midnight.
An update is needed before you can continue but you have more than one WaniKani tab open.
Finish up what ever you are doing on the other tab(s), then close them to continue.
The update will complete automatically once the other tab(s) are closed.