Wes dumps Hannah in a muddy waterhole and her clothes and hair get covered in mud. When she wakes up after their fight, her clothes and hair are clean.
During the final firefight, two bullet holes are made in the post above Ellie's head. However, when she turns and flees. the bullet holes are gone.
Multiple characters are carrying Colt Single Action Army revolvers (a.k.a. 'the Peacemaker'). The massacre at Silver Creek is said to have occurred three years earlier. As it occurred during the Civil War, the year can be no later than 1868. The Colt SAA was not available until 1873.
~40 minutes into the film they are playing Sloop John B, which was published in 1916.