According to Matt's narration, he, Frankie and Capt. Williams rode all night to get from town to a relay station and it is daylight when they get there. Yet they return to town very quickly and, also according to Matt's narration, it's too early for Plummer to be in his office. It should have taken all day for the return trip.
Even though the story is supposed to take place in the years 1863-1864, the revolvers used by the characters are of the design of the Colt .45 Single Action Army "Peacemaker" M1873 revolver, not in use in the 1860s.