diff --git a/features/esm.py b/features/esm.py
index 2b9ba67..13e1474 100644
--- a/features/esm.py
+++ b/features/esm.py
@@ -196,7 +196,9 @@ def classify_sessions_by_completion_time(
 
     Returns
     -------
-    object
+    df_session_counts_time: pd.DataFrame
+        A dataframe of all sessions (grouped by GROUP_SESSIONS_BY) with statuses, the number of items,
+            their time type (with some morning EMAs reclassified) and timestamp of first answer.
 
     """
     df_session_counts = classify_sessions_by_completion(df_esm_preprocessed)
@@ -204,8 +206,10 @@ def classify_sessions_by_completion_time(
 
     df_session_counts_time = df_session_time.join(df_session_counts)
 
-    df_session_counts_time.loc[
-        df_session_counts_time.esm_session_count > MAX_MORNING_LENGTH, "time"
-    ] = "daytime"
+    morning_transition_to_daytime = (df_session_counts_time.time == "morning") & (
+        df_session_counts_time.esm_session_count > MAX_MORNING_LENGTH
+    )
+
+    df_session_counts_time.loc[morning_transition_to_daytime, "time"] = "daytime"
 
     return df_session_counts_time