1To pass (of time); to elapse — used to indicate that a period of time has gone by since an event.
卒業してからもう五年が経った。
Five years have already passed since I graduated.
その出来事から数日が経ったが、まだ問題は解決していない。
Several days have passed since that incident, but the problem still hasn't been resolved.
しばらく経ってから返事をします。
I'll reply after some time has passed.