How to display a 'days since post' value next to post

Beginner with Ghost…

I’d like to add a bit of meta info next to posts, such as ‘300 days since this post was published, details may be outdated’, with the 300 being the crucial bit.

Momentjs seems to have something that would do it: Moment.js | Docs am I write in thinking this is baked in?

That being the case, how is this usually handled? A new handlebars helper? Or is there someway of doing this via the attributes?