Alan Webb born January 13, 1983, ran 3:53.43 on May 27, 2001 (18 years, 4 months, and 14 days old)
German Fernandez born November 2nd, 1990 ran 3:56.50 indoors on Jan 24, 2009 (18 years, 2 months, 22 days old)
So he's about 50 days younger than Webb when Webb ran that historic 3:53 mile!