経つ and 立つ: time passing and standing
Distinguish time passing from standing with the shared reading たつ, comparing elapsed time, future waiting time, and standing location.
How much time has passed
引っ越してから三か月が経ちました。 says that three months have passed since the move. 経つ, read たつ, has the elapsed time as subject, starting from the move.
時間が経つのは早いですね。 comments on how quickly time passes. It shares its reading with 立つ for standing, but elapsed time uses 経.
The next action after waiting
五分経ったら、もう一度電話してください。 asks someone to call again after five minutes. 五分 is the waiting duration, not the five-minute mark on a clock.
まだ一分しか経っていません。 means that only one minute has passed so far. Read しか with the negative; it does not mean that no time at all has passed.
Standing posture and spelling
入口に人が立っています。 says that someone is standing at the entrance. The subject is a person and に marks location, so the spelling is 立つ.
Both 経つ and 立つ have the forms たって and たった. Read 時間が経った and 人が立った with their subjects as well as their spellings to distinguish the identical sounds.
Does a request to call 五分経ったら mean calling immediately?
Show the answer and why
No. It means calling after five minutes have passed. 五分 is the duration to wait before acting.