How to update the Modified Date of folders with a batch file?

Question

copy /b Source+,, updates a file's Modified Date.

Is there a method for folders?

Answer 1

I can't see a simple way to change the date.
Neither renaming nor changing attributes has an effect on the modified date.

Currently, the only way seems to rename the directory, create a new one and move the content from the old to the new directory.
That's only a nasty solution.