Fix time-of-day-dependent failure in series_time validation (#395)

The series_time > content_time check was performed regardless of
whether series_date and content_date differed. When content_time
defaults to now.time(), this caused spurious failures depending on
what time of day the code (or tests) ran. The time comparison is now
only performed when the dates are equal.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: yarikoptic

src/highdicom/base.py

@@ -293,11 +293,15 @@ def __init__(
                     "'series_time' may not be specified without "
                     "'series_date'."
                 )
-            if content_time is not None:
-                if series_time > content_time:
-                    raise ValueError(
-                        "'series_time' must not be later than content time."
-                    )
+            if (
+                content_time is not None and
+                content_date is not None and
+                series_date == content_date and
+                series_time > content_time
+            ):
+                raise ValueError(
+                    "'series_time' must not be later than content time."
+                )
             self.SeriesTime = series_time
 
         if content_qualification is not None:

tests/test_base.py

@@ -99,12 +99,59 @@ def test_series_datetime(self):
             manufacturer_model_name='foo-bar',
             software_versions='v1.0.0',
             transfer_syntax_uid=ExplicitVRLittleEndian,
-            series_date=datetime.date(2000, 12, 1),
+            content_date=datetime.date(2024, 6, 15),
+            content_time=datetime.time(14, 0, 0),
+            series_date=datetime.date(2024, 6, 15),
             series_time=datetime.time(12, 34, 56),
         )
         assert hasattr(instance, 'SeriesDate')
         assert hasattr(instance, 'SeriesTime')
 
+    def test_series_datetime_earlier_date(self):
+        # series_time > content_time is fine when series_date < content_date
+        instance = SOPClass(
+            study_instance_uid=UID(),
+            series_instance_uid=UID(),
+            series_number=1,
+            sop_instance_uid=UID(),
+            sop_class_uid='1.2.840.10008.5.1.4.1.1.88.33',
+            instance_number=1,
+            modality='SR',
+            manufacturer='highdicom',
+            manufacturer_model_name='foo-bar',
+            software_versions='v1.0.0',
+            transfer_syntax_uid=ExplicitVRLittleEndian,
+            content_date=datetime.date(2024, 6, 15),
+            content_time=datetime.time(8, 0, 0),
+            series_date=datetime.date(2024, 6, 14),
+            series_time=datetime.time(23, 59, 59),
+        )
+        assert hasattr(instance, 'SeriesDate')
+        assert hasattr(instance, 'SeriesTime')
+
+    def test_series_time_after_content_same_date(self):
+        msg = (
+            "'series_time' must not be later than content time."
+        )
+        with pytest.raises(ValueError, match=msg):
+            SOPClass(
+                study_instance_uid=UID(),
+                series_instance_uid=UID(),
+                series_number=1,
+                sop_instance_uid=UID(),
+                sop_class_uid='1.2.840.10008.5.1.4.1.1.88.33',
+                instance_number=1,
+                modality='SR',
+                manufacturer='highdicom',
+                manufacturer_model_name='foo-bar',
+                software_versions='v1.0.0',
+                transfer_syntax_uid=ExplicitVRLittleEndian,
+                content_date=datetime.date(2024, 6, 15),
+                content_time=datetime.time(8, 0, 0),
+                series_date=datetime.date(2024, 6, 15),
+                series_time=datetime.time(12, 34, 56),
+            )
+
     def test_series_date_without_time(self):
         msg = (
             "'series_time' may not be specified without "