As of today - Friday, July 24, 2015 - 5,939 days have passed since Tuesday, April 20, 1999.
Here are the birthdays of all 15 people who died at Columbine High School on that date, and the number of days that each of them was alive:
Eric Harris - Thursday, April 9, 1981 - 6,585 days
Dylan Klebold - Friday, September 11, 1981 - 6,430 days
Dave Sanders - Monday, October 22, 1951 - 17,347 days
Isaiah Shoels - Monday, August 4, 1980 - 6,833 days
Lauren Townsend - Saturday, January 17, 1981 - 6,667 days
Rachel Scott - Wednesday, August 5, 1981 - 6,467 days
Cassie Bernall - Friday, November 6, 1981 - 6,374 days
Corey DePooter - Wednesday, March 3, 1982 - 6,257 days
Kyle Velasquez - Wednesday, May 5, 1982 - 6,194 days
John Tomlin - Wednesday, September 1, 1982 - 6,075 days
Kelly Fleming - Thursday, January 6, 1983 - 5,948 days
Matt Kechter - Saturday, February 19, 1983 - 5,904 days
Daniel Mauser - Saturday, June 25, 1983 - 5,778 days
Daniel Rohrbough - Friday, March 2, 1984 - 5,527 days
Steven Curnow - Tuesday, August 28, 1984 - 5,348 days
As of today, Matt Kechter, Daniel Mauser, Daniel Rohrbough, and Steven Curnow have been dead longer than they were alive.