All times are Monaco time (CEST). The countdowns use Monaco time even if your phone is set to another time zone.
To use it offline, open the page once with a connection, then add it to your home screen (Share, then Add to Home Screen on iPhone; the menu, then Install app on Android).
Changes are saved for everyone using the app.
Ticked groups that already have this visit are updated. Other ticked groups get it added.