If you wish to find the oldest file in a directory tree on a UNIX system, you might have found the following solution:

find . -type f -printf '%T+ %p\n' | sort | head -n 1

This is all good and nice, but it only works with the GNU version of findutils. Indeed other versions of find do not support the -printf option. A more compatible option goes something like that (it’s at the same time more generic (doesn’t use -printf) and more BSD specific (stat syntax) but you might adapt it to Linux easily):

find . -type f | xargs stat -f "%m %N" | sort | head -n 1