Since this word has okurigana (hiragana attached to the kanji) you know that it's probably going to be the kun'yomi reading, which you didn't learn with the kanji. Here's a mnemonic to help you:
We all want to change something. Probably a lotta (あらた) things! Think about all the things you want to change. Your name? Your habits? Your plans? The rules? The government? I bet you can think of a lotta things you want to change.
We decided to change the date.
You should correct that way of thinking.
Just as we discussed, we revised a part of the plan.