>>> idx = pd.date_range("2000-01-01", periods=3, freq="ns")
>>> idx
DatetimeIndex([ '2000-01-01 00:00:00',
'2000-01-01 00:00:00.000000001',
'2000-01-01 00:00:00.000000002'],
dtype='datetime64[ns]', freq=None)
>>> idx.nanosecond
Index([0, 1, 2], dtype='int64')