The exact moment, neither before nor after.
It always reminds us that God acts at all times, but mainly He acts at the right time, He never acted before or after.
There are times in life when we feel that there are things that are not right or that are not going the way we want them to go, this leads us to think that God is delaying or has forgotten us, but this text reminds us and gives us the assurance that God's plan is perfectly calculated.
Jesus came at the perfect time, in the time fulfilled by God's time, all this shows us that there is no difficulty, circumstance or anything else that is out of God's control, He has sent His Son Jesus Christ at the exact time to respect us and make us His children.
But when the time was fulfilled, God sent His Son, born of a woman and born under the law, to redeem those who were under the law, so that we might be adopted as sons.
Galatians 4:4-5