Converting values in date field to strings in text field using Python parser of ArcGIS for Desktop?

In the attribute table of my file geodatabase feature class I have a populated field called DateField of type date, and a text field called TextField.

I have not yet hit on a way to convert the dates in DateField to strings of mm/dd/yyyy format in the TextField.

I think this answer to Converting ArcGIS date value to string reading in mm/dd/yyyy format using ArcPy? should have given me enough clues, but when I try the following in the Field Calculator it results in the error that follows.

Parser: Python

Pre-Logic Script Code:

from datetime import datetime

def date_only(datetimeVal):
    formattedTime = datetime.strftime(datetimeVal, "%m/%d/%Y")
    return formattedTime

TextField =

date_only( !DateField! )

The error is:

Messages
Executing: CalculateField CountriesFC TextField date_only( !DateField! ) PYTHON_9.3 "from datetime import datetime\n\ndef date_only(datetimeVal):\n    formattedTime = datetime.strftime(datetimeVal, "%m/%d/%Y")\n    return formattedTime"
Start Time: Mon Feb 02 08:45:07 2015
ERROR 000539: Error running expression: date_only( u"13/02/2015 2:47:58 PM" ) 
Traceback (most recent call last):
  File "<expression>", line 1, in <module>
  File "<string>", line 4, in date_only
TypeError: descriptor 'strftime' requires a 'datetime.date' object but received a 'unicode'

Failed to execute (CalculateField).
Failed at Mon Feb 02 08:45:07 2015 (Elapsed Time: 0.03 seconds)

From the error I think that what I may be missing is the knowledge of how to convert the Unicode object that is being received by my date_only function into a datetime object.

Coincidentally, I noticed that there is currently a similar unanswered question on Stack Overflow: http://ift.tt/1KiHR4R