Sonnet 12

12

When I do count the clock that tells the time,

And see the brave day sunk in hideous night;

When I behold the violet past prime,

And sable curls all silvered o’er with white:

When lofty trees I see barren of leaves,

Which erst from heat did canopy the herd,

And summer’s green all girded up in sheaves

Borne on the bier with white and bristly beard:

Then of thy beauty do I question make,

That thou among the wastes of time must go,

Since sweets and beauties do themselves forsake,

And die as fast as they see others grow,

And nothing ‘gainst time’s scythe can make defence

Save breed to brave him, when he takes thee hence.

General
There are several works that WS kept for constant reference on his desk; one of them was Ovid's Metamorphoses, which it he knew both in the Latin and in Arthur Golding's 1567 translation – and, depending on the vocabulary/phraseology he uses we can sometimes tell which version he is thinking of at the time. Here, Book 15 ll. 221-237 applies, with its comparison of the passing of time in Nature and human life:

What? Seest thou not how that the yeere as representing playne
The age of man, departes itself in quarters fowre? First bayne
And tender in the spring it is, even like a sucking babe.
Then greene, and voyd of strength, and lush, and foggye, is the blade,
And cheeres the husbandman with hope. Then all things florish gay.
The earth with flowres of sundry hew then seemeth for to play,
And vertue small or none to herbes there dooth as yit belong.
The yeere from springtyde passing foorth to sommer, wexeth strong,
Becommeth lyke a lusty youth. For in our lyfe through out
There is no tyme more plentifull, more lusty, hote and stout. ...
Then followeth Harvest when the heate of youth growes sumwhat cold,
Rype, meeld, disposed meane betwixt a yoongman and an old,
And sumwhat sprent with grayish heare. Then ugly winter last
Like age steales on with trembling steppes, all bald, or overcast
With shirle thinne heare as whyght as snowe. Our bodies also ay
Doo alter still from tyme to tyme, and never stand at stay.
Wee shall not bee the same wee were today or yisterday.

(The full text of Golding's translation can be found at: http://www.elizabethanauthors.com/ovid15.htm) But you can also buy one – so much better for annotating – see Additional Reading blog (Jan 2010).

Time with its unstoppable tyranny, as we have already seen in Sonnets 2 & 5, is one of WS' major preoccupations. It is probably no accident that when the sequence was assembled, this sonnet was numbered 12, just as 30 and 60 are also concerned with the passing of time. This does, though, also have wider implications for the publication of the sonnets – who did it, who ordered them, and in particular whether Shakespeare knew about it. While I believe it is more appropriate to consider these sonnets not so much as a sequence as a collection, there are undeniable patterns and groups, some of which are centred on numbering.

Sense
First quatrain
The speaker says that when he counts the clock chimes telling the time and sees the splendid day sunk into obscure/fearful night; when he sees the violet past its best, and black hair turned to white....
1. tells: utters; counts/measures out. Both hearing and sight remind the speaker of the inexorable march of Time the Destroyer against ‘beauty’.
2. brave: resplendent
hideous: KDJ compares with Sonnets 5&6 and argues that there may be an association with hidden = causing dread or horror
3. violet: sometimes associated with faithfulness, WS uses the flower elsewhere, as KDJ points out, to do with the vulnerability of youth as in Hamlet 1.3.7ff (Laertes warning Ophelia about Hamlet's interest in her): 'A violet in the youth of primy nature, / Forward, not permanent, sweet, not lasting, / The perfume and suppliance of a minute.' More widely, it is also linked with the Virgin Mary as a symbol of her chastity.
past prime: past its best; when the spring is over; also originally associated with the first hour of the day and then by extension, spring or youth (KDJ). This from V&A, 131-2: 'Fair flowers that are not gathered in their prime / Rot and consume themselves in little time.'

The first quatrain is interesting for 1) its metre – the first line is all monosyllables, reflecting the ticking of a clock 2) the repetition of when, the time related word that will carry on into the second quatrain and 'convert' to then in the third.

Second quatrain
When the speaker sees tall trees bare of leaves, which formerly sheltered the herd from the heat, and summer’s greenery all bound up in sheaves, borne on the barrow, now turned white and bristly...
5. barren: unusual in the sense of barren leaves – more usually about fruit – recalls the chill landscape of bareness everywhere in 5.8 (CB); cf.11.10: barrenly perish. I wonder also if there is a reference to writing here, found in the pairing of barren and leaves - perhaps a sense of inspiration drying up.....writers, WS included (e.g Sonn 77) often use the metaphor of childbirth about their writing output.
6. canopy: this is its first cited use as a verb in the OED.
6-8. The combination of senses (of bier) turns harvest into a funeral, as the friend turns opportunities for reproduction into self-love (CB). There is also the Elizabethan idea of the harvest-home in which the last sheaf of grain was brought to the barn with great ceremony and celebration (SB).
Keats wrote in the margin of his copy of the sonnets, next to the account of summer’s bier: ‘Is this to be borne: Hark ye!’ [source: HV]
8. bier: a) handbarrow for carrying harvested grain; b) stand for a corpse cf. Hamlet 4.5.164: 'They bore him bare-faced upon the bier'.
beard: 'hair' (of such grains as wheat). It should perhaps be pronounced more like 'bird' – WS rhymes heard and beard in LLL 2.1.201/2.

Third quatrain
Then do I ask about the survival of your beauty, when you have to go ‘among the wastes of time’ – become one of the things destroyed by time, since virtue and beauty change/depart from themselves/give themselves up (to death)/lose their essential qualities, and decay/die just as quickly/steadily as they see others grow.

In her essay on this sonnet HV is most interested in the idea of sweets and beauties – esp sweets – she sees them as standing for inward virtue and outward show – ‘when we look back to see what proof we have for that interest in the poem, we behold, as if for the first time, the kindly trees sheltering the grateful herd’ – they stand for something sweet as well as participating in the list of ‘fading beauties’. She goes on: ‘The major aesthetic inventions of sonnet 12 are thus the decision to add sweets to beauties, and its corollary, the model of freely chosen acquiescence in one’s own death in favour of one’s children. ...If the young man is to be a creature of human worth, he must be virtuous, must not rail against but acquiesce morally in his own extermination, and must defy, by biologically reinforcing Nature’s increase, the power of Time to decrease value. Against the euphemistic view of Time by which things are said merely to sink or fade past their prime, the poem bravely faces up to the aggressive destructive power manifesting itself through Time the reaper; and against an aestheticism that would deplore only aging and the loss of beauty, the poem sets a moral elegy that deplores the eventual disappearance of sweet virtue, as well.’

I have found this interpretation of 'sweet' most useful when reading the sonnets (and elsewhere in WS). It gives more weight to a word that in the 21st century conjures images connected with pink and little girls. Here HV recognises that it has a completely different weight instead to do with measures of inner worth as well as outward beauty.
Couplet
Nothing can then take a stand against Time’s scythe, except to produce offspring to defy him when he takes you from this place.
13. breed: breed is a noun here = offspring, although there is the ‘hint of a desperate imperative’ (Burr).
14. brave: challenge/defy