History places the flood myths as a culture's way to explain the end of the last ice age. This happened about 10,000 years ago. But this book I'm reading (The Chronicles of the Imaginarium Geographica, Book 2, The Search for the Red Dragon) places Deucalion's flood (Greek flood) about 1,600 BC, the beginning of the Bronze Age. And that got me thinking, when (what year, if given) do mythologies place their flood myth?
The dates mentioned on Wikipedia's article on the subject concerning the historical basis of floods in myths (in chronological order):
It has been postulated that the deluge myth in North America may be based on a sudden rise in sea levels caused by the rapid draining of prehistoric Lake Agassiz at the end of the last Ice Age, about 8,400 years ago.
One of the latest, and quite controversial, hypotheses of long term flooding is the Black Sea deluge hypothesis, which argues for a catastrophic deluge about 5600 BC from the Mediterranean Sea into the Black Sea. This has been the subject of considerable discussion.
Another hypothesis is that a meteor or comet crashed into the Indian Ocean around 3000–2800 BC, created the 30-kilometre (19 mi) undersea Burckle Crater, and generated a giant tsunami that flooded coastal lands.
Excavations in Iraq have revealed evidence of localized flooding at Shuruppak (modern Tell Fara, Iraq) and various other Sumerian cities. A layer of riverine sediments, radiocarbon dated to about 2900 BC, interrupts the continuity of settlement, extending as far north as the city of Kish, which took over hegemony after the flood.
Speculation regarding the Deucalion myth has also been introduced, whereby a large tsunami in the Mediterranean Sea, caused by the Thera eruption (with an approximate geological date of 1630–1600 BC), is the myth's historical basis. Although the tsunami hit the South Aegean Sea and Crete, it did not affect cities in the mainland of Greece, such as Mycenae, Athens, and Thebes, which continued to prosper, indicating that it had a local rather than a regionwide effect.
Adrienne Mayor promoted the hypothesis that global flood stories were inspired by ancient observations of seashells and fish fossils in inland and mountain areas. The ancient Greeks, Egyptians, and Romans all documented the discovery of such remains in these locations; the Greeks hypothesized that Earth had been covered by water on several occasions, citing the seashells and fish fossils found on mountain tops as evidence of this history.
I hope this is answers your question or is otherwise informative.
PS: I recently answered Why did the gods use flooding to wipe out the human race? which is concerned with a related subject. It may be worth taking a look at.