pandas dt accessor error, column made with to_datetime not datelike?

问题

I am confused by an error returned by my Python script:

all_treatments['date'] = pd.to_datetime(all_treatments['INDATUMA'])
all_treatments['year'] = all_treatments['date'].dt.year

The error:

Traceback (most recent call last):
 File "treatments2_noiopro.py", line 93, in <module>
   all_treatments['year'] = all_treatments['date'].dt.year
 File "/home/seidav/anaconda/lib/python2.7/site-packages/pandas/core/generic.py", line 2145, in __getattr__
   return object.__getattribute__(self, name)
 File "/home/seidav/anaconda/lib/python2.7/site-packages/pandas/core/base.py", line 188, in __get__
   return self.construct_accessor(instance)
 File "/home/seidav/anaconda/lib/python2.7/site-packages/pandas/core/series.py", line 2528, in _make_dt_accessor
   raise AttributeError("Can only use .dt accessor with datetimelike "
AttributeError: Can only use .dt accessor with datetimelike values

What am I missing here?

I am using versions pandas 0.16.2 np19py26_0, iopro 1.7.1 np19py27_p0, and python 2.7.10 0 under Linux.

来源：https://stackoverflow.com/questions/31704221/pandas-dt-accessor-error-column-made-with-to-datetime-not-datelike