Twenty-three is hardly old, yet the speaker of this sonnet sounds like someone who has just realised he is late for something important. The poem opens on a gasp: "How soon hath Time, the subtle thief of youth, / Stoln on his wing my three and twentieth year!" Time is a burglar who has crept in so quietly that a whole year has gone before anyone noticed. The word "subtle" matters here, because the theft is only discovered once it is finished.
The first eight lines pile up images of speed and barrenness. Time has a "wing", the days are "hasting" and "fly on with full career", and "career" in Milton's day meant a horse's full gallop. Against all that motion the speaker sets a garden that has done nothing: "my late spring no bud or blossom shew'th." Then the complaint becomes more interesting. He admits that his "semblance might deceive the truth", since he may look nearly a man, while his "inward ripeness" lags behind that of other, "more timely-happy spirits." His worry is less about having achieved nothing than about what he is like inside. The sentence is also tangled. The verb "endu'th" is held back to the very end of the line, so the envy of those luckier people arrives last, like a small sting.
The form supports this mood. The octave runs on only two rhyme sounds in the pattern ABBAABBA, and the chain of "youth", "truth", "shew'th" and "endu'th" clinks together like a closed circle. The speaker seems to be going round and round in his own worry. The turn comes at line nine with "Yet", and the rhymes loosen into a sestet (CDEDCE) that has more room to move. The phrasing changes too. "Less or more, or soon or slow" is built from balanced pairs, so that the line itself is "even". When the speaker says his lot will arrive "in strictest measure even", the word "measure" may also point to metre, since the sonnet is itself a measured, balanced thing. That is a reading rather than a certainty, but the regular iambic pentameter does seem to calm down as the argument settles.
The most satisfying thing in the poem is what happens to Time. In line one Time is a thief, and by line twelve Time is the one "toward which Time leads me, and the will of Heaven." It is the same word with an opposite job: a robber has become a guide. The speaker never solves his problem by catching up with his rivals. He changes the yardstick instead. If his "lot, however mean or high" has already been fixed, being early or late stops being the right question.
The imagery shifts along with this. The seasonal language of spring, bud and blossom gives way to the language of work, and God becomes a "great Taskmaster". The word could sound harsh, but here it suggests an employer who sees everything and expects effort more than speed. The last line, "As ever in my great Taskmaster's eye", plays on "ever" meaning "always". The racing days of the opening are set against a gaze that never runs out. Even so, the speaker stays careful. "If I have grace to use it so" is a real condition, not a boast. His confidence rests on being watched and guided, not on any belief that he is already ripe.
Part of the poem's significance lies in its choice of subject. The sonnet is often a vehicle for love, but here it is used for self-doubt and the sense of a calling. Readers also know that its speaker belongs to the man who later wrote *Paradise Lost*, which gives its seriousness about "using" time and talent an extra weight, though the poem works perfectly well without that knowledge. Its enduring appeal is that the pressure it describes is easy to recognise. Anyone who has felt behind their classmates will see themselves in it, and the poem's answer is neither "work harder" nor "don't worry", but a quieter suggestion that the clock may not be the right judge.