Rename the file using the current system date

Here's how you'd rename the file using the current system date.

ren test.txt test%date:~4,2%-%date:~7,2%-%date:~10%.txt

or even better

ren test.txt test-%date:~4,2%-%date:~7,2%-%date:~10%-%time:~0,2%%time:~3,2%%time:~6,2%.txt