- This line basically says " you can see that time in year in me"

- "time of year" in him... Metaphor

- Shakespeare language behold meaning to see or observe

-The poet is like a tree with his decaying, worn out verses being dispersed in the wind.

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- "against" is used in the sense of anticipation

- shake against the cold = tremble in anticipation of cold days to come

- Choir was the spelling adopted from the word "quire" of the 17th century.

- See'st meaning to search, jump in.

- when the daylight, after sunset, fades away in the West'.

- "!sunset fadeth in the west"... Metaphor.

- fadeth means Third-person singular simple present indicative form of fade.

- by and by = fairly rapidly; soon

- Doth meaning Third-person singular simple presents a form of do; does

- translation: Night kills off the daylight, as a murderer kills his victim.

- Sleep is often portrayed as a second self of Death, or Death's brother.

- In this sonnet Night takes the place of sleep as the grand slayer

- a rhyme scheme here

-such fire = such as is seen at twilight; such as is described in the next line.

- his youth = the fire's youth. The possessive 'its' was not yet in use in Elizabethan England, so we should not assume that the word 'his' adds more to the sense of personification than if it had been 'its youth'.

-As the death-bed - the ashes of his youth are as a death-bed; whereon it must expire = on which it, the fire, or the youth, must at last die.

-Consumed with that = consumed, eaten away, at the same time as; eaten away by those things (which also nourish it). Similar to the line from Sonnet I :
Feeds thy light's flame with self-substantial fuel.
Life's progress from beginning to end is summed up in one line.

- Possibly a wish, rather than a statement of fact. 'When you perceive this, it will strengthen your love'. this presumably refers to the poet's waning life, described in the quatrains.