expression, noun
matter of time; question of time
Used to say that something will inevitably happen, and only the timing is uncertain. Often appears in the pattern ～は時間の問題だ.
彼が成功するのは時間の問題だ。
It's only a matter of time before he succeeds.
この古い橋が崩れるのも時間の問
It's probably just a question of time until this old bridge collapses.