A man sits on his porch reading and writing, and the warmth of the sun feels so good that he takes off his shirt without even thinking about it. Only afterward does he realize that he hasn't done this since he was seventeen. That small moment of surprise sets off the poem's bigger thought: life seemed to speed up after that age, and only now, at sixty-seven, is it finally slowing down.
The mood is relaxed, quietly joyful, and a little amazed. The short lines and sudden breaks mimic the speaker's unhurried, half-aware movements, and the gaps between lines feel like pauses to breathe. The "Ahhhhh" at the end works as a sigh of contentment, as if he has found a kind of peace he lost decades ago. Nothing dramatic happens, but the poem suggests that a simple physical pleasure can bring back a sense of youth and let a person feel time ease up.