diff --git a/cal_tools/cal_tools/tools.py b/cal_tools/cal_tools/tools.py
index f112c3cf089b62279ee18692ca719e37fd37ed7a..1b5707a3767f7934e92b218d591a214f70203a45 100644
--- a/cal_tools/cal_tools/tools.py
+++ b/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
diff --git a/tests/test_cal_tools.py b/tests/test_cal_tools.py
index 24d61719ce141e78e517e32cc02816e02228f40f..7fe26e12a9fb96a9a38f006311726da13ae46559 100644
--- a/tests/test_cal_tools.py
+++ b/tests/test_cal_tools.py
@@ -20,7 +20,7 @@ def test_dir_creation_date():
 
     date = get_dir_creation_date(folder, 9983)
     assert isinstance(date, datetime)
-    assert str(date) == '2020-09-23 13:30:50'
+    assert str(date) == '2020-09-23 13:30:50+00:00'
 
     with pytest.raises(ValueError) as e:
         get_dir_creation_date(folder, 4)