Decision made during the day yesterday with 〜うちに


Grammar Explanation

恋に恋するユカリちゃん » Volume 5 » Page 4

Yukari and her friends have a miscommunication on whether they’ll change from their summer uniforms to their winter uniforms yet. The decision is finalized just in time, as the following day is even colder.

ユカリ:
「昨日のうちに衣替えしておいて良かった。」
“I’m glad we (took the opportunity and) settled our uniform change (during) yesterday.”