いつのまにか
いつのまにか · itsunomanika · JLPT N3 · adverb
before one knows
⏳ いつの間にか = when + of + gap + ? — some point in time nobody noticed
Written with kanji it is いつの間にか: いつ (when) + の (of) + 間 ma (gap, interval) + に (in) + か (question marker). Literally: in the gap of when? You can't name the moment it happened, so it happened before you knew it.