Use Case
I just ran into a simple problem where I had to grep files on a server, but the directory had TONS and TONS of files in it. I just wanted to target files created within the last week or so.
Working Command
It turns out this find command is very handy for this occasion. It was taken and lightly modified from this unix stack-exchange post after a fair bit of searching.
find . -mtime -7 -exec grep "my_search_string" {} \;
Basically, it finds everything in “.” (the current directory) that was created in the last 7 days (as in 24 hour days, not from-this-morning days), and it executes the grep expression on it.
You can modify the timing however you want with mtime as well as change the target directory or command to execute, and of course you can pipe the output to whatever you want :).