The present January inaugural date is fixed by the 20th Amendment to the Constitution. Changing that would take years, not days.
But there is a way out - if our political leaders are smart, courageous, and public-spirited enough to take it.
Assume that Barack Obama wins the election, as polls show is increasingly likely. The following day, Vice President Cheney should be prevailed upon to resign. Using his powers to designate a successor under the 25th Amendment, President Bush should then appoint, and Congress should confirm, Obama as vice president (just as Richard Nixon appointed Gerald Ford vice president in 1973 when Spiro Agnew resigned). Bush himself should then resign, elevating Obama to the presidency - as Ford became president when Nixon resigned. Obama should then appoint Joe Biden as vice president.
With Congress's confirmation of Biden, the new administration would be in place, on the job, and ready to tackle the economic crisis - in November, not January. (The electoral college's official ratification of the election results in December would merely rubber-stamp the transition.)
While we're at it, why don't we repeal the 22nd Amendment in case The Obama desires a longer time in office than a mere two terms? And can't we just elect him to all three or four terms at once, rather than have a silly election every four years?