How long was Jeff in the rebel territory in Rifles for Watie?

In the short novel Rifles for Watie, Jeff lives in a rebel camp as an undercover Union officer for over a year. He spends a total of 4 years in service in the Civil War, from 1861 to 1865, beginning at just 16 years old. He starts out as a Union soldier and fights against what he feels are the callous, lawless southerners—the Confederates. To help the Union cause, he infiltrates a rebel Confederate camp and lives there for over a year. During this time, he begins to learn that the men on the other side of the trenches are just as human as his compatriots, and this drives home the point of the story and the Civil war—that brother fought against brother, and the war itself was cruel, even while it was fighting for glorious ideals.