Calendar and todo list view within the same page - ruby on rails

As the title suggests, I am working with a couple other students on a productivity app whose main functionality is shared between a calendar and a todo list. We want the main page of the web app to have two completely separate layouts with the calendar on one said and the todo list on the other - similar to the two panels on twitter.com (before logging in) but not equally sized.

I was experimenting with grids and flex from bootstrap, but I couldn't get the columns to extend to the full width and height of the page. What would be the correct implementation on a very basic website to have that kind of separation or is there a better approach? Thanks!