diff --git a/cheddahbot/tools/autocora.py b/cheddahbot/tools/autocora.py
index 62ecd1b..7818335 100644
--- a/cheddahbot/tools/autocora.py
+++ b/cheddahbot/tools/autocora.py
@@ -11,7 +11,7 @@ import json
 import logging
 import re
 import time
-from datetime import UTC, datetime
+from datetime import UTC, datetime, timedelta
 from pathlib import Path
 
 from . import tool
@@ -117,11 +117,8 @@ def _find_qualifying_tasks_sweep(client, config, categories: list[str]):
 
     # Current and last month tags (e.g. "feb26", "jan26")
     current_month_tag = now.strftime("%b%y").lower()
-    # Go back one month
-    if now.month == 1:
-        last_month = now.replace(year=now.year - 1, month=12)
-    else:
-        last_month = now.replace(month=now.month - 1)
+    # Go back one month (use 1st-of-current-month minus 1 day to avoid day-out-of-range)
+    last_month = now.replace(day=1) - timedelta(days=1)
     last_month_tag = last_month.strftime("%b%y").lower()
 
     # Fetch all "to do" tasks with due dates up to lookahead
diff --git a/tests/test_autocora.py b/tests/test_autocora.py
index bc0f6a2..259a164 100644
--- a/tests/test_autocora.py
+++ b/tests/test_autocora.py
@@ -442,13 +442,10 @@ class TestFindQualifyingTasksSweep:
         assert any(t.id == "t2" for t in result)
 
     def test_finds_last_month_tagged(self):
-        from datetime import UTC, datetime
+        from datetime import UTC, datetime, timedelta
 
         now = datetime.now(UTC)
-        if now.month == 1:
-            last = now.replace(year=now.year - 1, month=12)
-        else:
-            last = now.replace(month=now.month - 1)
+        last = now.replace(day=1) - timedelta(days=1)
         last_tag = last.strftime("%b%y").lower()
         # No due date needed for month-tag pass
         task = FakeTask(id="t3", name="Last Month", tags=[last_tag])