diff --git a/src/undate/undate.py b/src/undate/undate.py
index 96dd346..e816adb 100644
--- a/src/undate/undate.py
+++ b/src/undate/undate.py
@@ -331,8 +331,8 @@ def duration(self) -> datetime.timedelta:
                 duration = end - self.earliest.earliest
 
             # add the additional day *after* checking for a negative
-            else:
-                duration += ONE_DAY
+            # or after recalculating with adjusted year
+            duration += ONE_DAY
 
             return duration
 
diff --git a/tests/test_undate.py b/tests/test_undate.py
index 7293553..d02c3d2 100644
--- a/tests/test_undate.py
+++ b/tests/test_undate.py
@@ -264,11 +264,12 @@ def test_duration(self):
         month_noyear_duration = UndateInterval(
             Undate(None, 12, 1), Undate(None, 1, 1)
         ).duration()
-        assert month_noyear_duration.days == 31
+        assert month_noyear_duration.days == 32
+        # this seems wrong, but we currently count both start and dates
 
         # real case from Shakespeare and Company Project data;
         # second date is a year minus one day in the future
         month_noyear_duration = UndateInterval(
             Undate(None, 6, 7), Undate(None, 6, 6)
         ).duration()
-        assert month_noyear_duration.days == 364
+        assert month_noyear_duration.days == 365