diff --git a/niimpy/preprocessing/location.py b/niimpy/preprocessing/location.py
index d94973df..ff8b7379 100644
--- a/niimpy/preprocessing/location.py
+++ b/niimpy/preprocessing/location.py
@@ -520,6 +520,7 @@ def set_timezone(row):
     df = util.reset_groups(df)
     df["timezone"] = df.apply(get_timezone, axis=1)
     df = df.apply(set_timezone, axis=1)
+    df = util.select_columns(df, ["timezone"])
     return df