template_run_date to be Idempotent

Hi,

I used the **template_run_date** in one template, but this breaks my
tests. The task is not idempotent.

I did not found, how the **ansible_managed** works, that is idempotent,
my setup is like

ansible_managed = This file is managed by Ansible.%n
  template: {file}
  date: %Y-%m-%d %H:%M:%S
  user: {uid}
  host: {host}

Is there a way how to put the date of the generation into the file and
be idempotent when nothing else would change?

  thanks
    Peter