diff --git a/pygeoapi/api.py b/pygeoapi/api.py
index bfd75b2..8b83aa8 100644
--- a/pygeoapi/api.py
+++ b/pygeoapi/api.py
@@ -2556,10 +2556,15 @@ def validate_datetime(resource_def, datetime_=None):
 
         te = resource_def['temporal']
 
-        if te['begin'] is not None and te['begin'].tzinfo is None:
-            te['begin'] = te['begin'].replace(tzinfo=pytz.UTC)
-        if te['end'] is not None and te['end'].tzinfo is None:
-            te['end'] = te['end'].replace(tzinfo=pytz.UTC)
+        try:
+            if te['begin'] is not None and te['begin'].tzinfo is None:
+                te['begin'] = te['begin'].replace(tzinfo=pytz.UTC)
+            if te['end'] is not None and te['end'].tzinfo is None:
+                te['end'] = te['end'].replace(tzinfo=pytz.UTC)
+        except AttributeError:
+            msg = 'Configured times should be RFC3339'
+            LOGGER.error(msg)
+            raise ValueError(msg)
 
         if '/' in datetime_:  # envelope
             LOGGER.debug('detected time range')
diff --git a/tests/test_api.py b/tests/test_api.py
index e27d55d..669ff2f 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -503,6 +503,11 @@ def test_get_collection_items(config, api_):
 
     assert code == 200
 
+    rsp_headers, code, response = api_.get_collection_items(
+        req_headers, {'datetime': '2005-04-22'}, 'lakes')
+
+    assert code == 400
+
     rsp_headers, code, response = api_.get_collection_items(
         req_headers, {'skipGeometry': 'true'}, 'obs')