GNU date has some nifty options, and is a time keepers toolbox rolled up into an ELF executable. One really cool option in GNU date is the ability to print a date in the past using the the “–date” option, and the “days ago” format string:
date --date="30 days ago"
Wed Aug 30 15:15:51 EDT 2006
date --date="10 years ago"
Sun Sep 29 15:15:56 EDT 1996
Now if only more vendors would include GNU date with their operating system. :)