General console printout updates (#48)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

ultralytics/yolo/utils/files.py

@@ -1,5 +1,6 @@
 import contextlib
 import os
+from datetime import datetime
 from pathlib import Path
 from zipfile import ZipFile
 
@@ -61,3 +62,15 @@ def unzip_file(file, path=None, exclude=('.DS_Store', '__MACOSX')):
         for f in zipObj.namelist():  # list all archived filenames in the zip
             if all(x not in f for x in exclude):
                 zipObj.extract(f, path=path)
+
+
+def file_age(path=__file__):
+    # Return days since last file update
+    dt = (datetime.now() - datetime.fromtimestamp(Path(path).stat().st_mtime))  # delta
+    return dt.days  # + dt.seconds / 86400  # fractional days
+
+
+def file_date(path=__file__):
+    # Return human-readable file modification date, i.e. '2021-3-26'
+    t = datetime.fromtimestamp(Path(path).stat().st_mtime)
+    return f'{t.year}-{t.month}-{t.day}'