From the mighty Stack Overflow, some useful tips on using find with dates.
Bash - how to recursively find the latest modified file in a directory
Recursively finding the latest modified file in a directory.
Penguin Pete’s Blog - Using Bash To Solve A Brain Teaser
[Great use of Bash scripting to do a maths puzzle, but demonstrating lots of useful features.](http://penguinpetes.com/b2evo/index.php?title=using_bash_to_solve_a_brain_teaser&more=1&c=1&tb=1&pb=1)