The following verses discuss the time of the decree and punishment of the flood
• Gn05-32a states And Noah was 500 years old; and Noah fathered Shem, Ham, and Japheth...
• Gn06-01:03 states And it came to pass, when men began .... And the Lord said, My spirit shall not always strive with man, for he also is flesh; yet his days shall be a 120 years
• Gn07-06 states And Noah was 600 years old when the flood of waters was upon the earth.

Notice that Noah had children at 500 and the flood came when he was 600, a duration of 100 years. But God said yet his days shall be 120 years indicating that God would wait 120 years for man to repent. To account for this discrepancy between 100 and 120 years Rashi offers the following chronology
• Year 480 of Noah's life: Man is evil; God decrees destruction but gives mankind 120 years to repent
• Year 500 of Noah's life: Noah has 3 children
• Year 600 of Noah's life: The 120 years grace period is up; man does not repent; God brings the flood.

Advanced Rashi: Rashi, commenting on the 100-120 contradiction states There is no early and late in the Torah by which Rashi meant Biblical order is not chronological. Some students of Rashi capriciously interpret this to mean that Biblical order is random. Actually however the correct statement is There are several driving forces to Biblical order such as chronology, context, causality, etc. In other words Rashi was not seeking to indicate that the Biblical order arbitrary - rather he was trying to show that chronology is not the only determinant of Biblical order.

The order of these verses can be explained as follows
1. Gn05-01:32 describes the genealogies, lifespans and birthdates of 10 generations. The chapter concludes with the time - age 500 - that Noah gave birth to his children.
2. Gn06-01:09 describes the corruption that had emerged in the world and the facts that (a) God gave them a 120 year grace period to repent, (b) God intended to destroy the world by flood if man does not repent and (c) God would spare Noah who found grace in God's eyes.
3. Gn06-10... describes God's order to Noach to build an ark and be spared from the flood.

So we see that indeed the order is chronological! However it is chronological on paragraphs not on verses. First the genealogies (starting from Adam) are mentioned (Paragraph #1); then (paragraph #2) the corruption of the world and the impending doom; finally (paragraph #3) we read about Noah being saved by the ark.

We mention one more subtlety in the order. The last verse of paragraph #1, discussing Noah's birth at 500, is, in the Biblical notation, the first verse of paragraph #2, discussing how Noach would be saved from the corrupt world despite its corruption. This phenomenon of a terminal verse of one paragraph also functioning as the initial verse of a subsequent paragraph is called, in music, syncopation and is yet another principle of order. Syncopation is a powerful musical technique that tightly bounds a piece of music and provides cohesiveness.

Finally we point out that Rashi introduces additional material to explain the 480-500-600 year chronology. Pre-Torah people were not punished for their sins till after age 100 (Post Torah the punishment age is 20). Applying this to the 480-500-600 year chronology we see ....that Noah gave birth at age 500 while the flood came at age 600 implying that Noah's children were all age 100 or less and hence would not be punished by the flood. However Rashi's main point is that the warning to man came at Noah-age 480 while Noah's children came at age 500.