You don't have to add every single event to your calendar manually. Other people have already created a lot of calendars that contain events that matter to you: National holidays, football games, TV programs, etc.

All you have to do is add them to your own calendar.

Here's how you do it:

Tap at the top left to open the sidebar.
Scroll down to Add interesting calendars.
Select the calendars you want to be on your regular calendar.

Here are only a few examples of the calendars you can subscribe to (there are much more to them):

Public holidays
Religious holidays
NBA
NHL
Champions League
Moon phases
Name days
NASDAQ 100
TV Worldwide

Once you add the calendars you need, they'll appear as regular events.