Showcase #4 (the debut of the Barry Allen Flash and commonly acknowledged as the launchpad for the so-called "Silver Age of Comics") was dated Sept.-Oct. 1956 (Oct. on the cover). It went on sale approximately July 5, 1956.
Crisis on Infinite Earths #1 (the beginning of "the end" for the Silver Age DC Universe) was dated April 1985. It went on sale approximately January 3, 1985.
This week's DC Comics are dated July 2014. They went on sale today, May 7, 2014.
Crisis on Infinite Earths is older today than the entire Silver Age DC Universe was when Crisis on Infinite Earths began.