After Levi and Elly leave the wagon train and turn back, the voice over says the date is September 2nd. When the wagon wheel collapses and Elly is carving on the cliff face, the date reads August 11, 1845.
When Seccombe introduces Sam Puchas to the group, Purchas tells Levi to sell his horses and get oxen. Levi retorts, "like i told Major Mercy". Mercy is still a Captain and was introduced as such when he met Seccombe and the Zendts.