Do people need to register?

No. The flow is designed for quick entry, name selection, and marking days.

Is it useful for plans with friends?

Yes. That is the main use case: trips, dinners, hangouts, or informal meetups.

Can the participant list be changed later?

Yes. The organizer has a private URL to add or remove people.

Does the app highlight the strongest dates?

Yes. The overlap section ranks the dates with the best shared availability.