おも ったが吉日 きちじつ
omoitattaga kichijitsu

Expression

1. the best time for doing something is as soon as you've thought of it; there's no time like the present; it's an auspicious day (for doing it) when you've just had the idea — literal

Proverb
おも ったが吉日 きつじつ、さっそくプロジェクトの企画 きかく あん はじめよう。
omoitattaga kichijitsu sassoku purojekutono kikakuan'o kakihajimeyō.
Quick, let's get started on the project proposal while the idea is still fresh in our minds. There's no time like the present.
Other forms: