Since that time; from a particular event or point in the past up to now.
彼と会ってあれ以来、一度も連絡がない。
I met him and since then I haven't heard from him even once.
あの日の事故以来、彼女は車に乗らなくなった。
Since the accident that day, she stopped getting into cars.
2011年の出来事以来、地域の防災意識が高まった。
Since the events of 2011, the community's disaster-preparedness awareness has increased.