also: おもいたったがきちにち
expression
there's no time like the present; act on an idea right away
Proverb encouraging immediate action when inspiration strikes; literally 'the day you think of it is an auspicious day.'
旅行に行きたいと思ったら、思い立ったが吉日で、すぐに計画を立てよう。
If you feel like traveling, there's no time like the present—let's start planning right away.
思い立ったが吉日というから、新しい趣味を今日から始めることにした。
They say there's no time like the present, so I decided to start a new hobby today.
Similar meaning of 'strike while the iron is hot,' but 思い立ったが吉日 emphasizes acting on a personal idea or inspiration, while 善は急げ is more about not delaying a good deed or opportunity.
A Japanese proverb combining 思い立つ (to think of doing something) and 吉日 (auspicious day). The exact origin is uncertain, but it reflects a common cultural encouragement to act promptly on inspiration.