7 But the heavens and the earth, which are now, by the same word are kept in store, reserved unto fire against the day of judgment and perdition of ungodly men.
8 But, beloved, be not ignorant of this one thing (this sounds pretty important), that one day is with the Lord as a thousand years, and a thousand years as one day.
Ok, first of all God (through Peter) did not say, "one day is with the Lord as a billion years, and a billion years as one day." He said, "that one day is with the Lord as a thousand years, and a thousand years as one day." What does he mean here?
Well, what was he talking about? He is talking about the creation, judgment, and Jesus coming back.
Now remember that the Sabbaths "are a shadow of things to come". I believe that means,...the Sabbaths "are a shadow of things to come" (The annual Sabbaths and the weekly Sabbath). Peter here is giving us a key to unlock the shadow of the creation week. So, let us look closely to the creation week and relate it to a thousand years and the second coming of the Messiah.
Also, I do not hold God to exactly 1000 years for each day. I think it is an estimate. Other things that I think are estimates are statements like the one in Numbers 11:21: "And Moses said, The people, among whom I am, are six hundred thousand footmen; and thou hast said, I will give them flesh, that they may eat a whole month." Now when I get to His Kingdom, I am not going to call God a liar if I find out that it was actually 600, 021 footmen. In Physics we learn of the term Significant Figures. If we use significant figures in this verse, God could have anywhere between 550, 000 to 649,999 footmen. And if we use it in 2 Peter, a day could be anywhere between 500 to 1,499 years. So keep that in mind when I speak of a millennium.
Day 1: God separated the darkness and light
* saw the light, that it was good:
Shadow of the 1st millennium: God kicked Satan out of heaven and Adam learned the difference between good and evil.
Day 2: God divided the waters.
Shadow of the 2nd Millennium: The flood came and God divided the earth (separated the continents.)
Day 3:
9 And God said, Let the waters under the heaven be gathered together unto one place, and let the dry land appear: and it was so.
10 And God called the dry land Earth; and the gathering together of the waters called he Seas: and God saw that it was good.
11 And God said, Let the earth bring forth grass, the herb yielding seed, and the fruit tree yielding fruit after his kind, whose seed is in itself, upon the earth: and it was so.
12 And the earth brought forth grass, and herb yielding seed after his kind, and the tree yielding fruit, whose seed was in itself, after his kind: and God saw that it was good.
13 And the evening and the morning were the third day.
Shadow of the 3rd Millennium: God promised Abraham that through His seed, Jesus would reap a Harvest.
Day 4: God created the Sun.
Shadow of the 4th Millennium: Jesus came down and is the spiritual "light of the world" Jesus rules!
Day 5:
20 And God said, Let the waters bring forth abundantly the moving creature that hath life, and fowl that may fly above the earth in the open firmament of heaven.
21 And God created great whales, and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that it was good.
22 And God blessed them, saying, Be fruitful, and multiply, and fill the waters in the seas, and let fowl multiply in the earth.
23 And the evening and the morning were the fifth day.
Shadow of the 5th Millennium: Remember Peter's vision about the unclean animals, now being clean and Peter understood it to mean go witness to the Gentiles. (Maybe the 5th millenium has something to do with witnessing to the Gentiles and the multipling of the witness of the Gentiles?)
Day 6: God created the beast.
The Shadow of the 6th Millennium: The Beast (Anti-Christ will come and rule)
Day 7: God rested
Shadow of the 7th Millennium: We are going to rest in him for a thousand years commonly known as the millennium reign with Christ.
http://www.lamblion.com/prophecy/Jews-Israel/Jews-10.php
Because God's division of time into sevens, or weeks, so thoroughly permeates the Scriptures, the Jewish Rabbis concluded before the time of Jesus that human history would extend over a "Week of Millenniums," or for a period of 7,000 years.
According to the view most frequently expressed in the Talmud, there would be 6,000 years of human toil and strife followed by 1,000 years of peace. This Millennial Sabbath would be the period of the Messianic kingdom during which time the Messiah would reign in person over all the world from Jerusalem (Isaiah 24:21-23).
In other words, the Jews had concluded long before the book of Revelation was written that the Lord's reign on earth would last a thousand years. Revelation 20 confirmed this deduction by stating six times that the reign would last a thousand years.
The concept of the Millennium in the book of Revelation is therefore nothing new. The concept is rooted in the creation week of Genesis. It is reaffirmed in the week of feasts of Israel six feasts related to sin and toil leading up to a sabbath feast of rest.