Set backup date format for Ansible template module

How do you change the date format for files that Ansible’s template module creates when you use the backup option?

For example, the command:

template: src=supervisord.conf.j2 dest=/etc/supervisor/supervisord.conf backup=yes

creates a backup file: supervisord.conf.2015-08-24@12:17~

I’d like it to be something like: supervisord.conf.20150824_1217