GRAMMAR
いつの間にか
suddenly
unnoticed
Explanation
NOTE
いつの間にか means before I knew it or without realizing — describing a change or event that happened unnoticed by the speaker.
いつの間にか雨が止んでいた。
Before I knew it, the rain had stopped.
いつの間にか is an adverb. The 間 is read as ま, and it is often placed at the beginning or middle of a sentence.
NOTE
It conveys a sense of mild surprise — the speaker did not perceive the change as it was happening, and only notices the result.
NOTE
The following clause typically uses a past tense or 〜ている form to show a state that has already come about unnoticed.
STRUCTURE
いつの間にか+Clause
いつの間にか子供たちは大きくなっていた。
Itsu no ma ni ka kodomotachi wa ookiku natteita.
Before I knew it, the children had grown up.
空はいつの間にか暗くなっていた。
Sora wa itsu no ma ni ka kuraku natteita.
The sky had become dark before I noticed.
いつの間にか彼は部屋から出ていた。
Itsu no ma ni ka kare wa heya kara deteita.
Before I knew it, he had left the room.
Practice exercises
1
疲れていたので、横になった途端に、いつの間にか眠ってしまった。
I was tired, so the moment I lay down, I fell asleep unnoticed.
Answer
いつの間にか
2
本を読み始めたとたんに、いつの間にか時間が過ぎていた。
The moment I started reading, time passed unnoticed.
Answer
いつの間にか
3
新しいゲームを始める次第、いつの間にか時間を忘れてしまう。
As soon as I start a new game, I lose track of time unnoticed.
Answer
いつの間にか
4
考え事をしていたら、いつの間にか夜になっていた。
While I was deep in thought, it became night unnoticed.
Answer
いつの間にか
5
小説を読んでいると、いつの間にか夜明けになっていた。
As I was reading the novel, it became dawn unnoticed.
Answer
いつの間にか