Near the beginning of the movie when the outlaws are leaving Quinto for Texas, the newspaper lady watches them leave and then turns to write a column. The calendar on the wall shows the 1st on a Sunday and 31 days in the month. This could be March of 1891 or December of 1889; however, later in the movie the newspaper with the blank advertising block is dated September 21, 1890. So, the wall calendar in the newspaper office is incorrect (it's either the previous year - 1889- or the next year - 1891).
At the end of the movie a man states this is the end that Jesse James had been shot by Bob Ford and Frank James had been captured. While technically accurate, Jesse was killed over 10 years before the Coffeyville raid. Jesse was killed on Apr. 3, 1882 and the Coffeyville raid took place on Oct. 6, 1892.