It seems it returns different objects when passed array vs string: ``` In [1]: pd.to_datetime(['2012'])[0] Out[1]: Timestamp('2012-01-01 00:00:00', tz=None) In [2]: pd.to_datetime('2012') Out[2]: datetime.datetime(2012, 1, 1, 0, 0) ``` Also worth mentioning (though different): ``` In [3]: pd.Timestamp('2012') Out[3]: Timestamp('2012-06-13 00:00:00', tz=None) ``` Seems a little inconsistent... (cc #3859)