deep copies of Series with timezone-aware datetimes are shallow in 0.17.1: ``` python In [12]: import pandas as pd In [13]: pd.__version__ Out[13]: u'0.17.1' In [14]: ser = pd.Series([pd.Timestamp('2012/01/01', tz='UTC')]) In [15]: ser2 = ser.copy(deep=True) In [18]: ser2[0] = pd.Timestamp('1999/01/01', tz='UTC') # unexpected mutation In [19]: ser Out[19]: 0 1999-01-01 00:00:00+00:00 dtype: datetime64[ns, UTC] ```