code: def test_join_utc_convert(self, join_type):
      rng = date_range("1/1/2011", periods=100, freq="h", tz="utc")
  
      left = rng.tz_convert("US/Eastern")
      right = rng.tz_convert("Europe/Berlin")
  
      result = left.join(left[:-5], how=join_type)
      assert isinstance(result, DatetimeIndex)
      assert result.tz == left.tz
  
      result = left.join(right[:-5], how=join_type)
      assert isinstance(result, DatetimeIndex)
      assert result.tz is timezone.utc
  
file_path: pandas/pandas/tests/indexes/datetimes/test_join.py
imports: from datetime import datetime, timezone
  import numpy
  import pytest
  from pandas import DataFrame, DatetimeIndex, Index, Timestamp, date_range, period_range, to_datetime
  import pandas._testing
  from pandas.tseries.offsets import BDay, BMonthEnd
label_desc: Use image node_id 5 for calling the TestJoin obj's underlying member method code with example usage: obj.test_join_utc_convert(join_type) without return types