Nundina is a free online calendar. You keep your own events in it, with month, week and day views, and you can also subscribe to more than 200 public calendars that Nundina keeps up to date for you: football fixtures, Formula 1, NBA, anime and game release dates, public holidays, rocket launches, market and tax deadlines and more. A subscribed calendar updates itself, so when a fixture moves or a release slips, the entry in your calendar moves with it.
It is for people who already follow things that happen outside their own calendar: sports fans who check fixture lists, gamers and anime watchers who track release dates, investors watching market dates, and anyone tired of copying public holidays in by hand. It works signed out, keeping your data in your own browser, and signs in with Google, GitHub, Discord, Microsoft or an emailed code.
Nundina is free. The free plan covers your own calendar, up to 5 calendar subscriptions and 3 external ICS links, and browsing the public calendars needs no account at all. The optional Pro plan costs 1 USD per month and removes the subscription limit.
The usual alternatives are Google Calendar, Apple Calendar, Outlook Calendar, Notion Calendar, Fantastical and TimeTree. Those are calendars you fill in yourself, and Nundina works alongside them: it imports and exports ICS files and can sync with Google Calendar. What Nundina adds is the catalogue of public calendars that fill themselves, plus an AI assistant that creates and finds events in plain language.