Remove day.js as much as possible, use native date formatting

[mr-islam]

The native date formatting is amazing, and we should investigate it way more, specially for things like the simple date view.

For time calculations and display, we can keep more day.js I guess. (Changing this is a pain and needs loads of testing)

[mr-islam]

Just realized… this will help a lot with adding more languages! Since we don't need to manually import day.js support and also add to our bundle size. Rather, it would be built into the browser! (Also, check for browser support for this stuff!)