his sonnet contains the 14 lines that are significant of all Shakespeare's sonnets and it retains his style of having 3 quatrains with 4 lines in each and a couplet at the end of the sonnet.
The quatrains all have the basic underlying theme of the passing of human life from childhood to old age. It has been mentioned that this sonnet and earlier sonnets were written for the love of a young man but the theme of the sonnet is applicable in all human scenarios quite easily.
Like as the waves make towards the pebbled shore,
So do our minutes hasten to their end;
Each changing place with that which goes before,
In sequent toil all forwards do contend
The first quatrain uses imagery to compare human lives to the waves of the ocean and the movement of the waves as make their way towards the "pebbled shore" is similar to how the minutes of our human lives "hasten" towards our end. The pebbles of the shore indicate the hardships that we experience in our lives as time passes. There is a sequence to how our lives change and even though there might be other events that occur, the movement forward does not change with the passing of time.
Nativity, once in the main of light,
Crawls to maturity, wherewith being crown'd,
Crooked eclipses 'gainst his glory fight,
And Time that gave doth now his gift confound
The second quatrain describes how our "nativity" as Shakespeare puts it, or our birth and youth starts by being bright and the "main light" like the sun but gradually as time passes and we move towards maturity it is as if we start getting eclipsed. He compares this to the sun which "crawls" back and the glory of being crowned with the crown of youth is shadowed with age. He is comparing the passing of our lives to the movement of the sun as it rises in its full glory and light and is then eclipsed. It is as if there is a fight taking place for the sun to keep its glory or for us to keep our youth but to no avail as time that was once on our side now only confuses and defeats.
Time doth transfix the flourish set on youth
And delves the parallels in beauty's brow,
Feeds on the rarities of nature's truth,
And nothing stands but for his scythe to mow:
In the third quatrain Shakespeare describes how time can change the human face and the once "flourish" of youth is replaced with parallels on the brow. The word parallels means wrinkles and it is as he now comparing time to a monster with a scythe that is devouring the beauty and freshness of youth. Nothing can stop it or stand in its way as it mows or ages the person.
And yet to times in hope, my verse shall stand
Praising thy worth, despite his cruel hand.
In his last couplet, Shakespeare appears defiant and challenges time. Though there is not much that can be done to change the mortality of human beings his verse praising the object of his admiration or love will not change as time passes. He uses words like "cruel" to describe how time continues to pass with no regard for anything or anyone but he has "hope" that his words will stay unchanged and be left behind for all time.