currentTime is not supported on this instance of DataFrameTime??????????

Hi,

I keep getting an error in my script tool when trying to prompt the user to specify the time for a dataframe thats properties have not yet been set in the time slider window.

SCRIPT:
import arcpy
mxd = (GetParameterAsText(0))
df = arcpy.mapping.ListDataFrames(mxd)[0]
df.time.currentTime = arcpy.GetParameterAsText (1) #datetime.datetime(2009, 01, 1, 00, 00)
endTime = GetParameterAsText(2) # datetime.datetime(2009, 01, 1, 23, 59)


I need serious help!