You were right in believing that God created man on the sixth day. God ceased from all work on the seventh day, because He had finished the act of creating. He didn't "rest" because he was tired!
Note the order given early in Genesis...
Genesis 1:23 — Day 5 ends.
Genesis 1:24-2:1 — Day 6 events then the end of day 6.
Genesis 2:2-3 — Day 7, no work!
Genesis 1:23-2:3 And there was evening, and there was morning--the fifth day. 24 And God said, "Let the land produce living creatures according to their kinds: livestock, creatures that move along the ground, and wild animals, each according to its kind." And it was so. 25 God made the wild animals according to their kinds, the livestock according to their kinds, and all the creatures that move along the ground according to their kinds. And God saw that it was good. 26 Then God said, "Let us make man in our image, in our likeness, and let them rule over the fish of the sea and the birds of the air, over the livestock, over all the earth, and over all the creatures that move along the ground." 27 So God created man in his own image,in the image of God he created him;male and female he created them. 28 God blessed them and said to them, "Be fruitful and increase in number; fill the earth and subdue it. Rule over the fish of the sea and the birds of the air and over every living creature that moves on the ground." 29 Then God said, "I give you every seed-bearing plant on the face of the whole earth and every tree that has fruit with seed in it. They will be yours for food. 30 And to all the beasts of the earth and all the birds of the air and all the creatures that move on the ground--everything that has the breath of life in it--I give every green plant for food." And it was so. 31 God saw all that he had made, and it was very good. And there was evening, and there was morning--the sixth day. 2:1 Thus the heavens and the earth were completed in all their vast array. 2 By the seventh day God had finished the work he had been doing; so on the seventh day he rested from all his work. 3 And God blessed the seventh day and made it holy, because on it he rested from all the work of creating that he had done. (NIV)
Genesis 2:4 and on, is a recount of the events already stated providing more detail with a specific purpose. It should be noted that the first part of the book of Genesis is in a Hebrew poetical form [which we kind of miss in English]. Even as a writer now might go back to give more details after a summary, so too Moses did in this section of Genesis.
Genesis 2:4-7 This is the account of the heavens and the earth when they were created. When the LORD God made the earth and the heavens-- 5 and no shrub of the field had yet appeared on the earth and no plant of the field had yet sprung up, for the LORD God had not sent rain on the earth and there was no man to work the ground, 6 but streams came up from the earth and watered the whole surface of the ground-- 7 the LORD God formed the man from the dust of the ground and breathed into his nostrils the breath of life, and the man became a living being. (NIV)
Read Genesis 2:4 again and you will see that it is the introduction of an extra details section, the entire section where man's special position and creation is detailed. As such it had no need to go back and recount details given at the beginning. Rather, Genesis 2:7 provides clarifying detail to Genesis 1:26-27 and the following verses provide details to Eve's creation and their fall into sin.
Some have tried to discredit the start of Genesis because it's in a poetical form, claiming it to be "just a poem" and not history. In fact, many cultures in the world use poems to encompass and express their history. The style of the writing in no way takes away from the integrity of the contents. In fact, remembering a poem [as too with music] is a lot easier than other forms of writing. Perhaps the importance of understanding and remembering this entire section of Scripture [a foundation of everything else, including man's fall into sin and the need of redemption] is the very reason it was done in poetical form.
Other supporting passages of the Bible, showing that God was done by the seventh day, include...
Exodus 20:11 For in six days the LORD made the heavens and the earth, the sea, and all that is in them, but he rested on the seventh day. Therefore the LORD blessed the Sabbath day and made it holy. (NIV)
Exodus 31:17 It will be a sign between me and the Israelites forever, for in six days the LORD made the heavens and the earth, and on the seventh day he abstained from work and rested.'" (NIV)
Hebrews 4:3b-5 And yet His work has been finished since the creation of the world. 4 For somewhere He has spoken about the seventh day in these words: "And on the seventh day God rested from all His work." (NIV)
