script tool for df.time.currentTime ???

I'm getting this error when I run my script tool.


Traceback (most recent call last):
File "C:\Users\Courtney\Desktop\ScriptTool.py", line 233, in <module>
df.time.currentTime = arcpy.GetParameterAsText(6) #datetime.datetime(2009, 01, 1, 00, 00)
File "c:\program files (x86)\arcgis\desktop10.1\arcpy\arcpy\arcobjects\_base.py", line 92, in _set
(attr_name, self.__class__.__name__))
NameError: The attribute 'currentTime' is not supported on this instance of DataFrameTime.

Failed to execute (ScriptTool).

my code is :

df.time.currentTime = arcpy.GetParameterAsText(6) #datetime.datetime(2009, 01, 1, 00, 00)
endTime = arcpy.GetParameterAsText(7) #datetime.datetime(2009, 01, 1, 23, 59)
interval = arcpy.GetParameterAsText(8) #arcpy.time.EsriTimeDelta(1, 'hours')
#or #interval = datetime.timedelta(hours=1)

I don't understand why it says "currentTime" is not supported.

Any assistance is appreciated.

Thank you