§ Of Men The Silmarillion

From this time forth were reckoned the Years of the Sun. Swifter and briefer are they than the long Years of the Trees in Valinor. In that time the air of Middle-earth became heavy with the breath of growth and mortality, and the changing and ageing of all things was hastened exceedingly; life teemed upon the soil and in the waters in the Second Spring of Arda, and the Eldar increased, and beneath the new Sun Beleriand grew green and fair.