diff --git a/CHANGES.rst b/CHANGES.rst
index 19ef09ca..a433a73a 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,6 +1,8 @@
 Release 1.3.0
 =========================================
 
+* **BUGFIX:** Fixed incorrect serialization of datetime and Pandas ``Timestamp`` objects in ``.to_dict()`` and ``.to_json()`` (#74).
+* **BUGFIX:** Fixed incorrect serialization of ``EnforcedNull`` in ``.to_dict()`` and ``.to_json()`` (#75).
 * **ENHANCEMENT:** Added ``__repr__()`` method for Highcharts Core for Python classes (#76).
 * **ENHANCEMENT:** Added ``__str__()`` method with special handling for difficult-to-read classes (#76).
 * **ENHANCEMENT:** Added ``Chart.get_script_tags()`` to retrieve Javascript ``<script>`` tags (#78).
diff --git a/highcharts_core/metaclasses.py b/highcharts_core/metaclasses.py
index 350b5943..61ea9537 100644
--- a/highcharts_core/metaclasses.py
+++ b/highcharts_core/metaclasses.py
@@ -273,7 +273,10 @@ def trim_dict(untrimmed: dict,
                     as_dict[key] = trimmed_value
             # Enforced null
             elif isinstance(value, constants.EnforcedNullType):
-                as_dict[key] = 'null'
+                if to_json:
+                    as_dict[key] = None
+                else:
+                    as_dict[key] = value
             # dict -> object
             elif isinstance(value, dict):
                 trimmed_value = HighchartsMeta.trim_dict(value,
@@ -288,9 +291,23 @@ def trim_dict(untrimmed: dict,
                                                              context = context)
                 if trimmed_value:
                     as_dict[key] = trimmed_value
-            # Pandas Timestamp
-            elif checkers.is_type(value, 'Timestamp'):
-                as_dict[key] = value.timestamp()
+            # Datetime or Datetime-like
+            elif checkers.is_datetime(value):
+                trimmed_value = value
+                if to_json:
+                    if not value.tzinfo:
+                        trimmed_value = value.replace(tzinfo = datetime.timezone.utc)
+                    as_dict[key] = trimmed_value.timestamp() * 1000
+                elif hasattr(trimmed_value, 'to_pydatetime'):
+                    as_dict[key] = trimmed_value.to_pydatetime()
+                else:
+                    as_dict[key] = trimmed_value
+            # Date or Time
+            elif checkers.is_date(value) or checkers.is_time(value):
+                if to_json:
+                    as_dict[key] = value.isoformat()
+                else:
+                    as_dict[key] = value
             # other truthy -> str / number
             elif value:
                 trimmed_value = HighchartsMeta.trim_iterable(value,
@@ -440,7 +457,7 @@ def to_json(self,
                                  context = self.__class__.__name__)
 
         for key in as_dict:
-            if as_dict[key] == constants.EnforcedNull or as_dict[key] == 'null':
+            if as_dict[key] == constants.EnforcedNull or as_dict[key] is None:
                 as_dict[key] = None
         try:
             as_json = json.dumps(as_dict, encoding = encoding)
diff --git a/tests/test_metaclasses.py b/tests/test_metaclasses.py
index 4fa005a0..e8198d8c 100644
--- a/tests/test_metaclasses.py
+++ b/tests/test_metaclasses.py
@@ -8,6 +8,19 @@
 from json.decoder import JSONDecodeError
 from validator_collection import checkers
 
+try:
+    import orjson as json
+    json_as_bytes = True
+except ImportError:
+    json_as_bytes = False
+    try:
+        import rapidjson as json
+    except ImportError:
+        try:
+            import simplejson as json
+        except ImportError:
+            import json
+
 
 class TestClass(HighchartsMeta):
     """Class used to test the :class:`HighchartsMeta` functionality."""
@@ -396,7 +409,10 @@ def _get_kwargs_from_dict(cls, as_dict):
         if not error:
             obj = ClassWithTimestamp()
             result = obj.to_json()
-            assert 'timestamp_value' in result
+            if json_as_bytes:
+                assert b'timestamp_value' in result
+            else:
+                assert 'timestamp_value' in result
             as_dict = json.loads(result)
             assert 'timestamp_value' in as_dict
             assert checkers.is_numeric(as_dict['timestamp_value']) is True
@@ -405,6 +421,42 @@ def _get_kwargs_from_dict(cls, as_dict):
                 obj = ClassWithTimestamp()
 
 
+@pytest.mark.parametrize('error', [
+    (None),
+])
+def test_to_json_with_date(error):
+    from datetime import datetime, date
+    import json
+    
+    class ClassWithDate(HighchartsMeta):
+        @property
+        def date_value(self):
+            return date.today()
+        
+        def _to_untrimmed_dict(self, in_cls=None) -> dict:
+            return {
+                'date_value': self.date_value
+            }
+            
+        @classmethod
+        def _get_kwargs_from_dict(cls, as_dict):
+            return {}
+
+    if not error:
+        obj = ClassWithDate()
+        result = obj.to_json()
+        if json_as_bytes:
+            assert b'date_value' in result
+        else:
+            assert 'date_value' in result
+        as_dict = json.loads(result)
+        assert 'date_value' in as_dict
+        assert checkers.is_string(as_dict['date_value']) is True
+    else:
+        with pytest.raises(error):
+            obj = ClassWithDate()
+
+
 @pytest.mark.parametrize('instance, expected', [
     (test_class_camel_case_instance, "TestClassCamelCase(item1 = 123, item2 = 456, camel_case_item = 'test')"),
     (constants.EnforcedNull, "EnforcedNullType()"),
@@ -412,4 +464,35 @@ def _get_kwargs_from_dict(cls, as_dict):
 ])
 def test__repr__(instance, expected):
     result = repr(instance)
-    assert result == expected
\ No newline at end of file
+    assert result == expected
+
+
+class ClassWithEnforcedNull(HighchartsMeta):
+    @property
+    def enforced_null_value(self):
+        return constants.EnforcedNull
+    
+    def _to_untrimmed_dict(self, in_cls=None) -> dict:
+        return {
+            'enforced_null_value': self.enforced_null_value
+        }
+        
+    @classmethod
+    def _get_kwargs_from_dict(cls, as_dict):
+        return {}
+    
+    
+def test_enforced_null_to_dict():
+    obj = ClassWithEnforcedNull()
+    result = obj.to_dict()
+    assert 'enforced_null_value' in result
+    assert isinstance(result['enforced_null_value'], constants.EnforcedNullType) is True
+
+
+def test_enforced_null_to_json():
+    obj = ClassWithEnforcedNull()
+    result = obj.to_json()
+    if json_as_bytes:
+        assert result == b'{"enforced_null_value":null}'
+    else:
+        assert result == '{"enforced_null_value": null}'
\ No newline at end of file