find /tmp -mtime n where n can be +ve or -ve

+n says, file modified in last n days

-n says, file modified more than n days ago

ex. if today is 5th of a month

file1 has mtime 3rd

file2 has mtime 2nd

then find . -mtime 2 will report file1

then find . -mtime -2 will report file2 only