TO me, fair friend, you never can be old;  
For as you were when first your eye I eyed,  
Such seems your beauty still. Three Winters cold  
Have from the forests shook three Summers' pride;  
Three beauteous springs to yellow Autumn turn'd  
In process of the seasons have I seen,  
Three April perfumes in three hot Junes burn'd,  
Since first I saw you fresh, which yet are green.  
Ah! yet doth beauty, like a dial-hand,  
Steal from his figure, and no pace perceived;  
So your sweet hue, which methinks still doth stand,  
Hath motion, and mine eye may be deceived:  
   For fear of which, hear this, thou age unbred:  
   Ere you were born was beauty's summer dead.
William Shakespeare
http://www.poemhunter.com/poem/sonnets-xv/