While in the Calendar app you will have filter options on the menu to your left.
If you have access to a lot of widgets and collections, all of them will not show up in the list. Use Calendar search to find what you're looking for.
In the image above we have selected the board "New Board" and "Team engagements" for display.
Cards from "New Board" are coloured blue while cards from "Team engagements" are purple. Card color mirrors the board color.
Cards can be moved around freely in the Calendar view. Click and drag the right edge of your card to adjust its duration.
You can still edit cards while using the Calendar app.