Reading the subtitle of this topic I can't help but think that, on the contrary, there is archaeological evidence that Rome was founded in a day, and around the date given by the legend..
There is an important book to read about this by Alexandre Grandazzi called "The Foundation of Rome: myth and history. A detailed review can be found here:
http://ccat.sas.upenn.edu/bmcr/1998/98.4.02.html.

Sorry I don't remember how to put a link in here but here's an extract of the review.

"Grandazzi's answer (about the Foundation/eds)is both circumspect and stimulating. As Pierre Grimal puts it in his preface to the book, the author demonstrates on the one hand that history is a category of the mind. The history of early Rome was shaped through centuries by the need to recreate it. On the other hand Grandazzi sees one firm landmark in the vast field of myths and legends: the recent testimonies of archaeology, in particular the excavations at the Palatine led by Andrea Carandini between 1985 and 1988.
The oldest strata found there, which date from 730-720 B.C. and consist of a wall, a palisade and an empty space in between, remind us obviously of the famous pomoerium of Romulus. Grandazzi is very impressed by these excavations and calls them "a breach in the wall between myth and reality". This statement -- made right at the beginning of the book -- shows that Grandazzi's methodological discourse basically serves as an evaluation of Carandini's discoveries. His aim is to reconcile the literary tradition on early Rome with this archaeological evidence."