Look at this passage from Pink's Sovereignty of God

The context of the whole chapter might be needed, but I suspect this passage can stand on its own:

"A brief word now concerning the extent of human responsibility [responsibility in salvation, i.e. to repent and so on and call on God].

It is obvious that the measure of human responsibility varies in different cases, and is greater or less with particular individuals. The standard of measurement was given in the Saviour’s words, "For unto whomsoever much is given, of him shall much be required" (Luke 12:48). Surely God did not require as much from those living in Old Testament times as He does from those who have been born during the Christian dispensation. Surely God will not require as much from those who lived during the ‘dark ages,’ when the Scriptures were accessible to but a few, as He will from those of this generation, when practically every family in the land own a copy of His Word for themselves. In the same way, God will not demand from the heathen what He will from those in Christendom. The heathen will not perish because they have not believed in Christ, but because they failed to live up to the light which they did have—the testimony of God in nature and conscience."

This is very much the same thing Zwingli believed (he believed Socrates was saved, for instance). It is a position that is lost in much Calvinist discourse. I have to admit to allowing myself to get into unnecessary knots in defending Calvinist doctrine when in fact it is - biblically - much looser than the tight mathematical treatise its critics paint it as so as to knock it down.

(And on the subject of heathens and those without the Bible and so on I also see time as a factor, i.e. higher aspects of time, recurrence, the fact that God can act in a person's life from eternity and is not constrained by our limited perception of time; the fact that the 'fullness of time' is a pregnant phrase in Scripture which suggests a filling out of time including an individual's time in a higher way, etc., and unbelieving at death doesn't necessarily mean reprobate at death.)

In this same chapter (chapter 8) Pink also describes the process of turning to God in a way Arminians would say "A hah! that is not Calvinism!" when it is. You have to read it. He says what I on my own in going back and forth with people came to: the Word of God is the wild card in the process...