Change name of email in marketing activities folders?

We have a naming convention for our content stream emails as above that is YYYY.MM.DD

The content we had originally planned for today is going through some unexpected revisions and I was wondering if there was a way to change the name of an email that was already created, or is this permanent? We'd like to change one of these to 2015.04.09.

This is strictly for our own view in Marketo (and not the email subject line).