The -mtime option can be used to return files and directories that were modified x or more days ago. For example, to return files and directories that were modified 14 or more days ago below the tmp directory.
find /tmp -mtime +14
For example, to return files and directories that were not modified 14 or more days ago below the tmp directory.
find /tmp ! -mtime +14
To include the date and time the file was last modified in the output.
find /tmp -exec stat --format "%y %n" "{}" \;
This will return something like this.
2020-07-06 05:50:18.594805437 -0500 /tmp/foo.txt
2020-07-06 02:10:38.898884577 -0500 /tmp/bar.txt