From the story:
Ennis woke in the red dawn with his pants around his knees, a top-grade headache, and Jack butted against him; without saying anything about it both knew how it would go for the rest of the summer, sheep be damned.
As it did go. They never talked about the sex, let it happen, at first only in the tent at night, then in the full daylight with the hot sun striking down, and at evening in the fire glow, quick, rough, laughing and snorting, no lack of noises, but saying not a goddamn word except once Ennis said, "I'm no queer," and Jack jumped in with "me neither. A one-shot thing. Nobody's business but ours."
It suggests a passage of time.