Creation Ended 6th or 7th Day?

In Genesis 2:2, many bibles say that Yahweh completed his creation activity on the seventh day.

And on the seventh day God ended his work which he had made...
--KJV
And on the seventh day God finished his work that he had done...
--ESV

Other bibles translate it "by the seventh day" instead of "on" or "in" the seventh day so that the days of creation are six full days instead of six full days and part of the seventh.

What is less known is that the word seven appears in the Masoretic texts, but not the Septuagint or Samaritan Pentateuch. These other textual traditions, which antedate our Masoretic texts and their families by 1,000 years and more, say that God completed his creation activity on/in the sixth day.

And God finished on the sixth day his works which he made...
--LXX

The sixth day translation would be the superior except for the fact that both the Samaritan Pentateuch and the Septuagint are translations of the Hebrew. In order to verify this as the correct ancient wording, what we need is a Hebrew script from ancient times which agrees with these other ancient texts against the late Masoretic ones. For that, we turn to the Dead Sea Scrolls. Unfortunately, the only words preserved in 4QGen are the words "...his...which...".

All right then, what of the Targumim--the Aramaic translations? Targum Onkelos, our oldest and most trusted, says "And the Lord finished in the Seventh Day His work which He had wrought."

The Vulgate also supports the "seventh" day, but the Peshitta says "sixth."

In the absence of a DSS witness, it is hard to make a decision. But due to the presence of at least one ancient authority reading "seventh day" (Targum Onkelos), I'm going to have to go with "seventh" as the original reading because it is the more difficult reading. The preceding days began and ended in their respective orders, making us believe creation took six days. It would be easier for a scribe to change the text to say "sixth" in harmony with the last chapter than to go out of his way to say creation went over into the seventh day when it originally said sixth.