import os, sys
from datetime import datetime

oldest = datetime.max
newest = datetime.min
oldest_file = None
newest_file = None

if os.lstat in os.supports_dir_fd:
    for dir, _, files, dirfd in os.fwalk(sys.argv[1]):
        for file in files:
            mtime = os.lstat(file, dir_fd=dirfd).st_mtime
            date = datetime.fromtimestamp(mtime)
            if date < oldest:
                oldest = date
                oldest_file = os.path.join(dir, file)
            if date > newest:
                newest = date
                newest_file = os.path.join(dir, file)
else:
    print('not using dir_fd')
    # for dir, _, files in os.walk(sys.argv[1], followlinks=False): ...

print('Newest:', newest.strftime('%Y-%m-%d %H-%M-%S'), newest_file)
print('Oldest:', oldest.strftime('%Y-%m-%d %H-%M-%S'), oldest_file)