For those interested in the proposed dates for the historical Buddha, one might summarize them as follows:
Traditional Theravadin dates: 623/4-543/4 B.C.E. (rejected by scholars)
From the Dotted Record Chronology: 566-486 B.C.E. (fallen out of favor, according to Dr. Prebish)
From the Corrected Long Chronology: 563-483 B.C.E. (fallen out of favor)
Ryusho Hikata: 508-428 B.C.E. (rejected by virtually all scholars, acccording to Dr. Prebish)
From the Short Chronology (advocated by Heinz Bechert): 448-368 B.C.E.
Andre Bareau: 500/460-420/380 B.C.E.
U.I. Hakuju: 466-386 B.C.E.
Hajime Nakamura: 463-383 B.C.E.
Richard Gombrich (most recently proposed dates): 484-404 B.C.E.
The most plausible date ranges for the Buddha's life given at a symposium at the University of Gottingen in 1988 seem to be: 484-404 B.C.E., 448-368 B.C.E., and 463-383 B.C.E. Most arguments hinge on the question of how many years (100? 116? 218?...) passed from the Buddha's death to the relatively firm date of the coronation of King Asoka. (Asoka's accession date is derived from references to foreign rulers whose dates are known in an Asokan edict carved in rock. His coronation date was probably approximately 268 B.C.E., although it might have been anywhere from 280-267. The Buddha's birth would then be 80 years before the date of the Buddha's death, based upon the univeral testimony of the various ancient traditions.)
An article summarizing recent research may be found here:http://www.buddhistethics.org/15/prebish-article.html