Change "date added" attribute of a file

Hello!

I have been using Terminal to change the "date added" attribute of a file without success.

What I'm doing is:

#1. Display the attributes of a file:

mdls file_name

#2. Display the "date added" attribute:
xattr -p "kMDItemDateAdded" file_name

#3. Change it:

sudo xattr -w "kMDItemDateAdded" "201111111111.11" file_name

The third instruction does not work! Where as touching the file with the same date value DOES change date modified.

Any ideas from the community?

Kind regards,

Elias.