diff --git a/CHANGELOG.md b/CHANGELOG.md
index d8ed24c064e..85c4e05bacb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,13 @@ All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
 
+## [4.14.3] - UNRELEASED
+
+### Fixed
+
+- `px.timeline()` now allows `hover_data` formatting of start and end times [3018](https://github.com/plotly/plotly.py/pull/3018)
+
+
 ## [4.14.2] - 2021-01-11
 
 ### Updated
diff --git a/packages/python/plotly/plotly/express/_core.py b/packages/python/plotly/plotly/express/_core.py
index d29b90b46c3..fe362c7e1a1 100644
--- a/packages/python/plotly/plotly/express/_core.py
+++ b/packages/python/plotly/plotly/express/_core.py
@@ -375,9 +375,10 @@ def make_trace_kwargs(args, trace_spec, trace_data, mapping_labels, sizeref):
                     trace_patch[error_xy] = {}
                 trace_patch[error_xy][arr] = trace_data[attr_value]
             elif attr_name == "custom_data":
-                # here we store a data frame in customdata, and it's serialized
-                # as a list of row lists, which is what we want
-                trace_patch["customdata"] = trace_data[attr_value]
+                if len(attr_value) > 0:
+                    # here we store a data frame in customdata, and it's serialized
+                    # as a list of row lists, which is what we want
+                    trace_patch["customdata"] = trace_data[attr_value]
             elif attr_name == "hover_name":
                 if trace_spec.constructor not in [
                     go.Histogram,
@@ -398,6 +399,13 @@ def make_trace_kwargs(args, trace_spec, trace_data, mapping_labels, sizeref):
                     for col in attr_value:
                         if hover_is_dict and not attr_value[col]:
                             continue
+                        if col in [
+                            args.get("x", None),
+                            args.get("y", None),
+                            args.get("z", None),
+                            args.get("base", None),
+                        ]:
+                            continue
                         try:
                             position = args["custom_data"].index(col)
                         except (ValueError, AttributeError, KeyError):
@@ -408,9 +416,10 @@ def make_trace_kwargs(args, trace_spec, trace_data, mapping_labels, sizeref):
                             position
                         )
 
-                    # here we store a data frame in customdata, and it's serialized
-                    # as a list of row lists, which is what we want
-                    trace_patch["customdata"] = trace_data[customdata_cols]
+                    if len(customdata_cols) > 0:
+                        # here we store a data frame in customdata, and it's serialized
+                        # as a list of row lists, which is what we want
+                        trace_patch["customdata"] = trace_data[customdata_cols]
             elif attr_name == "color":
                 if trace_spec.constructor in [go.Choropleth, go.Choroplethmapbox]:
                     trace_patch["z"] = trace_data[attr_value]
diff --git a/packages/python/plotly/plotly/tests/test_core/test_px/test_px_input.py b/packages/python/plotly/plotly/tests/test_core/test_px/test_px_input.py
index eeb28283649..477e7dbcb04 100644
--- a/packages/python/plotly/plotly/tests/test_core/test_px/test_px_input.py
+++ b/packages/python/plotly/plotly/tests/test_core/test_px/test_px_input.py
@@ -309,7 +309,8 @@ def test_pass_df_columns():
         marginal="rug",
         hover_data=tips.columns,
     )
-    assert fig.data[1].hovertemplate.count("customdata") == len(tips.columns)
+    # the "- 2" is because we re-use x and y in the hovertemplate where possible
+    assert fig.data[1].hovertemplate.count("customdata") == len(tips.columns) - 2
     tips_copy = px.data.tips()
     assert tips_copy.columns.equals(tips.columns)