I just read in Cross, David. Data Munging with Perl (Greenwich, CT: Manning, 2001) that Unix measures time elapsed since Thursday, January 1st 1970. It measures it in seconds. Try this command on a Unix box or Macintosh running OSX.

perl -e "print time";

for user friendly time

perl -e "print scalar localtime";

When was a billion seconds?

perl -e "print scalar localtime(1_000_000_000)";

that's all btw this date is very close to September 11, 2001. Does this mean that Unix is involved in terrorism?