Now we have sufficient data to calculated the time required to cross the terrible terrain just north of Lehi-Nephi. Alma and his people traveled eight days before they settled in the valley of Helam. Later, the Lord put the Lamanites to sleep and after one full day of travel, Alma and his people camped in the valley of Alma. But they did not get to stay there overnight. In a forced march of twelve days, they finally arrived in the land of Zarahemla and king Mosiah welcomed them with great joy.
Based on this specific data we can calculate that a body of people with their flocks traveled a total of 21 days to reach their goal of crossing the narrow strip of wilderness and coming out into the valley of Sidon or Zarahemla.