Decision made during the day yesterday with 〜うちに

Grammar Explanation: During with 〜うちに

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(きのう)のうちに衣替(ころもが)えしておいて良(よ)かった。」; “I'm glad we (took the opportunity and) settled our uniform change (during) yesterday.”

Key Points

昨日のうちに means within yesterday
- The uniform decision was made while yesterday was still the available window.
- うちに highlights doing something before that time passed.
しておいて良(よ)かった says the preparation paid off
- 衣替(ころもが)えしておく means to get the uniform change settled in advance.
- 良(よ)かった shows relief now that the next day is colder.
The timing matters more than the duration
- This is not about something happening throughout yesterday.
- It means the action was completed before yesterday ended.