いつぞや

adverb

some time ago; the other day; once

Refers vaguely to a past occasion, often when the speaker cannot recall the exact time. Can also be used in a rhetorical or polite way to refer to a previous meeting.

• いつぞやは大たい変へんお世せ話わになりました。

  Thank you very much for your help the other day.

• いつぞやそんな話はなしを聞きいた気きがする。

  I feel like I heard that story some time ago.