Fix/keep time zone info 3.1.0

cal_tools/cal_tools/tools.py

@@ -275,7 +275,8 @@ def get_dir_creation_date(directory: Union[str, Path], run: int,
             rfile = sorted(rfiles, key=path.getmtime)[0]
             with h5py.File(rfile, 'r') as fin:
                 cdate = fin['METADATA/creationDate'][0].decode()
-                cdate = datetime.datetime.strptime(cdate, "%Y%m%dT%H%M%SZ")
+                cdate = datetime.datetime.strptime(cdate,
+                    "%Y%m%dT%H%M%SZ").replace(tzinfo=datetime.timezone.utc)
             return cdate
         except (IndexError, IOError, ValueError):
             ntries -= 1