expression, godan verb (-tsu)
time passes; time goes by
Neutral expression for the passage of time. Often used when noting how long something has taken or that a certain amount of time has elapsed.
あれからもう三年の時間が経った。
Three years have already passed since then.
時間が経つのは早いものだ。
Time flies.
Similar meaning, but 過ぎる can imply time passing beyond a certain point or excessively. 経つ is more neutral about the simple passage of time.
Compound of 時間 (time) + が (subject marker) + 経つ (to pass, elapse). The verb 経つ is a native Japanese word for the passage of time.