Great question!  I have wondered about this, too.  Here’s my best attempt at an answer. It obviously would have had to have occurred sometime after the point that God had created Adam himself; because there would have had to have been enough time for Adam to till the ground of the garden that God had placed him in (Genesis 2:15); which would have been before the curse, when the work of the ground would result in toil of labor (3:17-19).  And there would also have had to be the time necessary to name the animals, which was something that Adam did before Eve was created (2:19-20).  So, I’m suspecting that the real question would be how much time that transpired between Eve’s creation and Eve’s temptation in the garden; because Adam would have had some time to get to know her and appreciate that she was his true helpmeet (2:23), and for them to live life together in such a way as to be ‘unashamed’ (v. 25). I have heard some say that it happened almost immediately — the very day Eve was created.  But I’m not sure how this can be known for certain.  Instead, I suspect that there must have been at least some amount of time that transpired after Eve’s creation before she ate; because she must have had time to dialogue with the serpent without being surprised by the fact that a serpent spoke, and for her to have been taught that the tree was forbidden to her, and for her to have looked upon the fruit and be tempted by it.  When she said, in Genesis 3:13, that the serpent “beguiled” her, the verb is put in the Hebrew Hiph’il stem (a causative form); which expresses the idea that the serpent ’caused’ the action of eating to be done by Eve. How long such a thing might have taken isn’t told to us in the Genesis story.  But two other New Testament passages might help.  First, in 2 Corinthians 11, the apostle Paul wrote to the Corinthian believers and said;

Oh, that you would bear with me in a little folly—and indeed you do bear with me.  For I am jealous for you with godly jealousy.  For I have betrothed you to one husband, that I may present you as a chaste virgin to Christ.  But I fear, lest somehow, as the serpent deceived Eve by his craftiness, so your minds may be corrupted from the simplicity that is in Christ.  For if he who comes preaches another Jesus whom we have not preached, or if you receive a different spirit which you have not received, or a different gospel which you have not accepted—you may well put up with it! (2 Corinthians 11:1-4).

How long might it possibly have taken for believers—taught the truths of the gospel by Paul—to theoretically have been corrupted by it in their thinking, or for them to receive something willingly that was the opposite of what they had been taught?  It probably wouldn’t have happened immediately; but they might possibly have been confused by false teaching and persuaded against the truth over a period of time.  It could be that, in the same way, Eve had to have been corrupted in her thinking by the devil over a process of time. Another passage that might help is 1 Timothy 2:13-14;

For Adam was formed first, then Eve.  And Adam was not deceived, but the woman being deceived, fell into transgression (1 Timothy 2:13-14).

I think it’s fascinating that though Eve was deceived, Adam ate of the fruit with complete knowledge of what he was doing.  We’re told that “She also gave to her husband with her, and he ate” (Genesis 3:6).  It doesn’t seem possible that Adam—who had clearly heard the command of God first hand (while Eve would have only heard it second hand from Adam)—would have had his commitment to the command persuaded away from him abruptly, since he had heard the command not to eat directly from God Himself.  And for two people to fall together—one who had been deceived in ignorance and the other persuaded with full knowledge—would have, it seems to me, taken some time. In the end, of course, we simply can’t know for sure.  But since the Bible doesn’t tell us clearly, it’s probably not too important.  The key thing that the story in the Bible is meant to convey to us is that the temptation had indeed occurred, was in fact yielded to, and that humanity fell, and we are all under the curse as a result.  Praise God that Jesus—”the Lamb slain from the foundation of the world” (Revelation 13:8)—has died for us and redeemed us from the curse! Blessings, Pastor Greg