diff --git a/CHANGES.rst b/CHANGES.rst
index a45504d5..a6c783ef 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,3 +1,11 @@
+Release 1.2.1
+=========================================
+
+* **ENHANCEMENT:** Added autoconversion of ``plotLine.value`` from ``datetime.datetime`` to POSIX timestamp (#58).
+* **BUGFIX:** Fixed incorrect ``datetime`` serialization to SECONDS from Unix epoch. Now serializing to JS-compatible MILLISECONDS from Unix epoch (#61).
+
+------------------
+
 Release 1.2.0
 =========================================
 
@@ -25,6 +33,8 @@ Release 1.1.1
 * **FIXED:** Problem when producing a JS literal, with the JS code inserting an unnecessary ``new`` (#42 and #43).
 * **ENHANCEMENT:** Added more elegant error handling when something goes wrong displaying a chart in Jupyter (#43).
 
+-------------
+
 Release 1.1.0
 =========================================
 
diff --git a/highcharts_core/__version__.py b/highcharts_core/__version__.py
index e916218b..ce34e913 100644
--- a/highcharts_core/__version__.py
+++ b/highcharts_core/__version__.py
@@ -1 +1 @@
-__version__ = '1.2.0'
\ No newline at end of file
+__version__ = '1.2.1'
\ No newline at end of file
diff --git a/highcharts_core/js_literal_functions.py b/highcharts_core/js_literal_functions.py
index 15019c50..914fba01 100644
--- a/highcharts_core/js_literal_functions.py
+++ b/highcharts_core/js_literal_functions.py
@@ -49,7 +49,7 @@ def serialize_to_js_literal(item, encoding = 'utf-8') -> Optional[str]:
     elif checkers.is_datetime(item):
         if not item.tzinfo:
             item = item.replace(tzinfo = datetime.timezone.utc)
-        return item.timestamp()
+        return item.timestamp()*1000
     elif checkers.is_date(item):
         return f'Date.UTC({item.year}, {item.month - 1}, {item.day})'
     elif checkers.is_time(item):
diff --git a/highcharts_core/options/axes/plot_bands.py b/highcharts_core/options/axes/plot_bands.py
index 4c276af1..b2bfabe6 100644
--- a/highcharts_core/options/axes/plot_bands.py
+++ b/highcharts_core/options/axes/plot_bands.py
@@ -349,6 +349,9 @@ def value(self) -> Optional[int | float | Decimal]:
 
     @value.setter
     def value(self, value):
+        if hasattr(value, 'timestamp'):
+            value = value.timestamp() * 1000
+
         self._value = validators.numeric(value, allow_empty = True)
 
     @property
diff --git a/highcharts_core/options/plot_options/series.py b/highcharts_core/options/plot_options/series.py
index 9f2074b6..04a0de72 100644
--- a/highcharts_core/options/plot_options/series.py
+++ b/highcharts_core/options/plot_options/series.py
@@ -797,10 +797,10 @@ def point_start(self, value):
             value = validators.datetime(value)
 
             if hasattr(value, 'timestamp') and value.tzinfo is not None:
-                self._point_start = value.timestamp()
+                self._point_start = value.timestamp()*1000
             elif hasattr(value, 'timestamp'):
                 value = value.replace(tzinfo = datetime.timezone.utc)
-                value = value.timestamp()
+                value = value.timestamp()*1000
             else:
                 raise error
             
diff --git a/highcharts_core/options/plot_options/treegraph.py b/highcharts_core/options/plot_options/treegraph.py
index 6d85957f..8797c8b5 100644
--- a/highcharts_core/options/plot_options/treegraph.py
+++ b/highcharts_core/options/plot_options/treegraph.py
@@ -491,10 +491,10 @@ def point_start(self, value):
             value = validators.datetime(value)
 
             if hasattr(value, 'timestamp') and value.tzinfo is not None:
-                self._point_start = value.timestamp()
+                self._point_start = value.timestamp()*1000
             elif hasattr(value, 'timestamp'):
                 value = value.replace(tzinfo = datetime.timezone.utc)
-                value = value.timestamp()
+                value = value.timestamp()*1000
             else:
                 raise error