Here's the only thing I can find I've ever used re renaming - the first is just one line and uses the same input file name each time
Rename ""C:\Test.TXT"",""C:\Test.""+DTE(0:""%Mz%Dz%Y"")
Then this one prompts for a name
INPUT 'CS',@(20,20),""File Name....:"", N$
Rename ""C:\""+N$,""C:\""+N$+DTE(0:""%Mz%Dz%Y"")