Space.com reports that astronomers have revised the date of the original Battle of Marathon, moving it forward a month from September 12, 490 B.C. Like the original marathon runner, Pheidippides, the marathoners in the 2004 Olympics will have the excruciating heat of August to contend with.
Marathon Man : Astronomer Sleuths Revise Date of Ancient Rome.
More of The Run of Pheidippides and whether or not he actually ran the marathon on any date.