Shell Scripting Recipes: A Problem-Solution Approach, from Apress, is geared towards Unix users who don't want to waste time testing and creating shell scripts. Since most of these scripts are POSIX-based, they are supported by Bash, ksh and sh, among others.
Chapter 8 -- The dating game -- of Shell Scripting Recipes: A Problem-Solution Approach provides over a dozen functions for manipulating and formatting dates.
Chapter 8, "The Dating Game," is excerpted from Shell Scripting Recipes: A Problem-Solution Approach by Chris A. Johnson, published in May 2005, by Apress (ISBN: 1-59059-471-1). Copyright © 2005, Apress. All rights reserved. Reprinted with permission by Apress.