莎士比亚的第十二行诗如下：
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.
这首诗是莎士比亚十四行诗第12首，通常被称为“晨颜”或“时间的流逝”。诗中通过对时间流逝的描绘，表达了对生命短暂和美丽的感慨。