diff --git a/services/scheduler/app.py b/services/scheduler/app.py
index 523a15c..5eb774f 100644
--- a/services/scheduler/app.py
+++ b/services/scheduler/app.py
@@ -125,8 +125,16 @@ def is_source_due(
     if last_status == "failed":
         if retry_count >= MAX_RETRY_COUNT:
             return False
-        if next_retry_at and now < next_retry_at.replace(tzinfo=None):
-            return False
+        if next_retry_at:
+            # Normalize tz-awareness to match 'now'
+            if now.tzinfo is not None and next_retry_at.tzinfo is None:
+                nra = next_retry_at.replace(tzinfo=timezone.utc)
+            elif now.tzinfo is None and next_retry_at.tzinfo is not None:
+                nra = next_retry_at.replace(tzinfo=None)
+            else:
+                nra = next_retry_at
+            if now < nra:
+                return False
         # Backoff elapsed or no next_retry_at set — allow retry
         return True
 
@@ -139,7 +147,12 @@ def is_source_due(
         return True
 
     cadence = get_cadence_for_source(source_type, source_config)
-    elapsed = (now - last_completed_at.replace(tzinfo=None)).total_seconds()
+    # Ensure both datetimes have matching tz-awareness for subtraction
+    if now.tzinfo is not None and last_completed_at.tzinfo is None:
+        last_completed_at = last_completed_at.replace(tzinfo=timezone.utc)
+    elif now.tzinfo is None and last_completed_at.tzinfo is not None:
+        last_completed_at = last_completed_at.replace(tzinfo=None)
+    elapsed = (now - last_completed_at).total_seconds()
     return elapsed >= cadence