That's easy.
If you are hung up on the 4350-year thing, the entire question is silly.
The age of the earth has increased by over 100% since "science" put a number to its formation. That never invalidated that the earth came into existence sometime in the past. The earth is not eternal, no one has suggested that.
Well, neither is the "scientific" (factual) age of the "flood" or "floods".
First things first.
I'm not "hung up" on the 4350 date; I think the global flood is entirely mythical, with a massive amount of scientific evidence arguing against any such event anywhere close to 4350 years ago.
But the 4350 year date is what I find Biblical scholars and creationists prefer. According to a variety of sources, the date of the global flood was:
2252 BC -- layevangelism.com
2304 BC -- Answers in Genesis (+/- 11 years).
2350 BC -- Morris, H. Biblical Creationism. Grand Rapids, MI: Baker Books, 1993.
2370 BC -- TalkOrigins.com
2500 BC -- http://www.nwcreation.net/biblechrono.html
2522 BC -- Dr. Gerhard Hasel
2978-3128 BC -- http://www.asa3.org/archive/ASA/199605/0162.html
3300 BC -- http://www.biblediscoveries.com/flood1.html
3537 BC -- Setterfield (1999)
Here is some additional information: Problems with a Global Flood, Second Edition, by Mark Isaak.