diff --git a/craft_application/util/cli.py b/craft_application/util/cli.py
index 8ee7769a..a56e52ca 100644
--- a/craft_application/util/cli.py
+++ b/craft_application/util/cli.py
@@ -16,6 +16,7 @@
 """CLI-related utilities."""
 
 import datetime
+import warnings
 
 
 def format_timestamp(dt: datetime.datetime) -> str:
@@ -34,4 +35,9 @@ def format_timestamp(dt: datetime.datetime) -> str:
     else:
         # timezone naive, assume it's UTC
         dtz = dt
+        warnings.warn(
+            "Timezone-naive datetime used. Replace with a timezone-aware one if possible.",
+            category=UserWarning,
+            stacklevel=2,
+        )
     return dtz.strftime("%Y-%m-%dT%H:%M:%SZ")
diff --git a/tests/unit/util/test_cli.py b/tests/unit/util/test_cli.py
index a45fb572..d10adb97 100644
--- a/tests/unit/util/test_cli.py
+++ b/tests/unit/util/test_cli.py
@@ -20,6 +20,12 @@
 
 from craft_application.util import format_timestamp
 
+pytestmark = [
+    pytest.mark.filterwarnings(
+        "ignore:Timezone-naive datetime used. Replace with a timezone-aware one if possible.",
+    )
+]
+
 
 @pytest.mark.parametrize(
     ("dt_obj", "expected"),