起きたこと

what happened

→ 起きる
phrase Uncommon #12,000
what happened Refers to an event or events that have already occurred.
JA: 起きたことを忘れないで。
EN: Don’t forget what happened.

新しく起きたこと。

Something new that happened.

それは随分昔に起きたことです。

That happened a very long time ago.

起きたことの理由の解明で

In figuring out why it happened

— オープン・ユア・アイズ (1997)

わたしに起きたことがわたしのせいじゃなくても、校長はきっと気に入らないだろう。

Even if what happened to me wasn't my fault, the principal probably won't be happy about it.