@panchan9 the date-fns is currently not supported by cli’s default requirejs setup.
I could not figure out how to config date-fns to work. I worked on cli tracing code before, so you can take the answer as (almost) negative. But @JeroenVinke might help.
Anyway there is a way out. If you use cli + webpack, it definitely works. (au new proj, choose 3.Custom -> 3.Webpack).