Perfect

Perfect indicates a completed past action which produced results which are still in effect up to the present.

ἐὰν εἴπωμεν ὅτι οὐχ ἡμαρτήκαμεν ψεύστην ποιοῦμεν αὐτὸν καὶ ὁ λόγος αὐτοῦ οὐκ ἔστιν ἐν ἡμῖν
If we say that we have not sinned, we make him a liar, and his word is not in us.
Υἱός μου εἶ σύ ἐγὼ σήμερον γεγέννηκά σε
You are my Son, this day I have begotten you