Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.

Later Reminders - Super simple way to schedule reminders on your phone

Eventbrite - Discover Great Events or Create Your Own & Sell Tickets

Reminder - A better way to keep track of your reminders 📝

Calendify - Calendify is an event community where you can share, publish, and subscribe to event calendars. It helps you to stay informed about what you are interested in and what is yet to come.

doo - A smart, simple app for reminders and to-dos