diff --git a/pages/data_explorer.py b/pages/data_explorer.py
index c76c5de..e3a13c7 100644
--- a/pages/data_explorer.py
+++ b/pages/data_explorer.py
@@ -321,6 +321,7 @@ def _corr(df):
                 st.error(f"Transformation error: {exc}")
             else:
                 st.session_state["data"] = df_trans
+                st.session_state["datetime_cols"] = eda.detect_datetime_columns(df_trans)
                 data = df_trans
                 st.success("Transformations applied!")
 
diff --git a/tests/test_pages.py b/tests/test_pages.py
index bd321bf..e80aa0d 100644
--- a/tests/test_pages.py
+++ b/tests/test_pages.py
@@ -111,3 +111,23 @@ def test_time_series_page_contents():
     assert "time_series_plot" in content
     assert "decomposition_plot" in content
 
+
+def test_datetime_cols_persist_after_transforms():
+    import streamlit as st
+    from utils import transform, eda
+
+    df = pd.DataFrame(
+        {
+            "date": pd.date_range("2021-01-01", periods=3, freq="D"),
+            "value": [1.0, 2.0, 3.0],
+        }
+    )
+    st.session_state.clear()
+    st.session_state["data"] = df
+
+    df_trans = transform.scale_features(df.copy(), ["value"], method="standard")
+    st.session_state["data"] = df_trans
+    st.session_state["datetime_cols"] = eda.detect_datetime_columns(df_trans)
+
+    assert st.session_state["datetime_cols"] == ["date"]
+