Looking for files older than n number of days?

[Francisco Reyes]

On Sun, 5 Jun 2005, Dan Nelson wrote:

> "find . -mtime +5" , or "find . -mtime +5d", depending on whether you
> want 5 days as of the next midnight, or 5 days as of when find was
> started.

How do those flags work?
+5 = changed during last five days?
-5 = newer than five days?

I ran it on a directory and was surprised to find that both -5 AND +5 
listed a file from February. :-(