An analysis of John Milton's “How Soon Hath Time” will look at both the poem's structure and content, including its form, subject matter, and literary devices.
The poem is a sonnet with the standard fourteen lines in iambic pentameter (five poetic feet per line with an unstressed-stressed pattern for each foot) and a rhyme scheme that scans abbaabbacdedce. Notice that this rhyme scheme is slightly different from most sonnets in its second half, but Milton is bending the form to make it his own.
In terms of subject matter, Milton is reflecting on time and how it continues to pass with no stopping. Milton is just finishing his twenty-third year here, yet it already seems to him that his youth is passing rapidly away. He doesn't look like he has “arriv'd so near” to manhood, nor does he feel as though he has that “inward ripeness” that indicates maturity and that some of his peers possess. Yet Milton knows well that time proceeds “in strictest measure” no matter what he looks or feels like. Time leads him on to his destination according to “the will of Heav'n.” His job is to make use of God's grace under God's eyes.
Milton uses many literary devices as he pursues his ideas. For instance, he calls time a “subtle thief of youth” who steals his twenty-third year and flies away with it. His days, too, fly by, and he feels as though he is living in “late spring” with his buds and blossoms disappearing. These are all delightful and apt metaphors. The phrase “inward ripeness” is also metaphoric and suggests maturity in terms of fruit.
Further, Milton tends to personify time in this poem. It is, as we said, a thief, but it is also a leader, guiding Milton on to his fulfillment under God's watchful eyes. Notice, too, how Milton capitalizes “Time,” making the word into a proper name.